Mass murder in the Czech Republic
On 21 December 2023, 14 people were killed and 22 injured in a mass shooting at the main Faculty of Arts building of Charles University in central Prague, Czech Republic. Another three people were injured when the perpetrator opened fire toward the streets from the faculty's fourth-floor rooftop terrace. After having been engaged by the police, the perpetrator, 24-year-old postgraduate student David Kozák, committed suicide by shooting himself. 
At the time of the shooting, the perpetrator was one in a pool of about 4,000 suspects in a double murder case that took place six days earlier, away, when a father and his infant daughter were murdered in Klánovice. The lead investigator confirmed that the police had not yet reviewed the perpetrator's potential as a suspect in the earlier killings when the Prague shootings took place. Evidence from the shootings linked the two incidents. The shooter's father was also found shot dead at his home in Hostouň.
The attack was the deadliest mass murder in the Czech Republic since its independence in 1993, surpassing the 2020 Bohumín arson attack.
Events.
Klánovice Forest murders.
On 15 December 2023, a 32-year-old father and his two-month-old daughter in a stroller were shot dead in Klánovice Forest on the eastern outskirts of Prague, approximately away from where the later Charles University attack would take place. The police conducted a detailed search of the entire forest with hundreds of officers, while a special task force was set up in order to find the perpetrator. The police had no direct leads. The scope of investigation was first directed at owners of registered firearms matching the ballistic report from the crime scene, which initially limited the search to about 30,000 people. This was then further limited to 4,000, of which about 40 people lived in direct vicinity of the Klánovice Forest. The initial investigation focused on those 40 people brought no leads. On 20 December, police said that they had no leads in the case but were continuing to search for the perpetrator.
Once a personal or work related motive was exhausted, the police search focused on the possibility of a random murder. The firearms website zbrojnice.com noted a similarity of the case with the 2005 "Forest Killer" murders, in which a former police officer killed three random victims in forests in preparation for a planned mass murder in the Prague Metro, which was prevented by his early arrest; the article ended with an appeal to readers to remain vigilant and carry their concealed firearms.
Later investigation revealed that the perpetrator had previously visited the Klánovice Forest only once. On the day of the University attack, Kozák had written a suicide note on his computer detailing the Klánovice murders, and had hidden the murder weapon in the family garden. According to the letter, he used public transport on the day of the murders and switched off his phone while changing transport on the other side of the City of Prague. Kozák was armed with two handguns— a Glock 45 and a Beretta 71— as well as a silencer.
Kozák initially wanted to target a woman with two children at a playground along the main forest path, but then he noticed a man with a stroller heading towards side path off the main trail and decided that he was an easier target. Kozák followed him closely for a while before shooting the man multiple times using the Glock 45 pistol. He then murdered the baby with two more rounds before fleeing the scene. Kozák fled on foot towards Úvaly, leaving the forest first by bus, and then switching to a train. At some point during his escape, Kozák passed by a couple with a stroller and considered shooting them as well, but decided not to after hearing sirens in the distance.
The chief detective of Prague's 1st General Crime Unit stated because Kozák lived in the Central Bohemian Region, they were a few days short of being able to prevent the University attack. Central Bohemia is a separate region from the city of Prague, and each region in the country has a separate police directorate.
Hostouň patricide and police manhunt.
On 21 December 2023 at 12:19 CET, the Central Bohemian Police received a call from Kozák's mother. At 12:20 CET, Kozák's female friend "K.C." called medical emergency line, stating that Kozák was planning to take his own life, that "he could be dangerous", that he told her "he will do something she will hear about", and that he was on route from his hometown of Hostouň to Prague. At 12:33, the police entered Kozák's home and found the body of his father, who was killed by three shots into the head. The father was shot from behind while sitting at a table. His neck was then laid on a block of wood, and an axe lying next to him indicated that Kozák intended to cut his father's head off, which he didn't do. A thorough search of the house at this time was hindered by improvised explosive devices, which were decommissioned by specialists later that day. The police found out that Kozák was a student of the Faculty of Arts at Charles University in Prague. A search warrant was issued and published; the warrant indicated that Kozák was armed and dangerous.
At 13:10 CET the Central Bohemian Police, where the Kozák's home was located, directly alerted the City of Prague Police. Prague police dispatcher issued an APB, according to which Kozák was sought due to suicide threats, he may be dangerous and also may be connected to a violent crime, possibly a murder. A security operation was commenced at Václav Havel Airport Prague, where Kozák worked, and where his father worked in the airport security department.
At 13:20 CET, Prague Police checked the Central Registry of Firearms, noting that Kozák owns multiple firearms, and that one of them was of the type which was the focus of Klánovice murders investigation. The APB was expanded with information that Kozák should be considered extremely dangerous.
At 13:23 CET the perpetrator entered the main building of the Faculty of Arts on Jan Palach Square with a heavy suitcase through the busy main entrance without arousing any suspicion. He proceeded to the fourth floor bathrooms, where he apparently remained until the start of the attack. In the suitcase, he brought firearms, a large amount of ammunition, cleavers, chains and bicycle locks. Before starting the attack, the perpetrator placed his ID, fourth floor plan with handwritten notes about classrooms capacities, unopened alcohol bottle, and Rivotril pack of medicine under the bathroom window. 
At 13:30 CET, two police units, altogether six officers, entered the main building of the Faculty of Arts on Jan Palach Square, where they talked to the reception personnel as well as to two Vice-Deans whom they met in the corridors. One of the officers searched premises of the campus library and adjacent bathrooms. They further searched through the ground floor and first floor, where they visited the Student Affairs Office and Department of History and learned about Kozák's lecture schedule, according to which he was supposed to attend a lecture starting at 14:00 in a different building on Celetná street.
At 13:57 CET, the dispatch sent multiple police units to evacuate the building of the Faculty of Arts on Celetná street, including the six police officers from the main building, who left without taking any further action there, and who would later stand guard at the Celetná building until the start of the attack in the main building. The Celetná building is a twelve-minute walk from the main building at Jan Palach square. The evacuation of Celetná building was finished at 14:22. Kozák was not found in the building or in its vicinity. Multiple students walked from evacuated Celetná building into the main building.
At 14:04 CET, the dispatch relayed the following information through the police radio transmitter: "Increased caution for all patrols in the case of this Kozák. He's a really dangerous, very dangerous offender, suspect, and there's a lot of concern that he could use a weapon anytime, anywhere."
At 14:38 CET, Kozák's phone was turned on and registered by a telecommunications tower located near the Old Jewish Cemetery about 100 meters from the main building. The manhunt continued on the street level in this area, including Jewish Quarter, Pařížská street, the Old Town Square and Staroměstská metro station. Dozens of heavily armed police officers, including Prague SWAT unit, spread out in the crowded area where Christmas markets were taking place.
Some plain-clothed criminal detectives moved from the Celetná building into the wider area of Jan Palach square in front of the main building. They did not enter the main building, as they had information that it had already been searched by other police units.
Charles University shooting.
At 14:54, the perpetrator exited the 4th floor restroom armed with a pistol and opened fire inside the building's fourth floor corridors and classrooms. He repeatedly entered classroom No. 423, targeting everyone inside. Once he moved further away from this classroom, one of the students led remaining survivors to barricade the door. All of the people in this classroom were either killed or suffered life-threatening injuries. The perpetrator also entered classroom no. 417 on the same floor and opened fired on those present.
At 14:57:28 CET, the first phonecall about the attack on the 4th floor of the Faculty of Arts building on Jan Palach square reached the medical emergency line. Police first received information about the attack at 14:59:06. At 15:02 CET the first officer, a criminal police detective, entered the building, with uniformed policemen joining him at 15:03 CET and dozens more afterwards. After the arrival of the police, no gunshots were heard from within the building, which led the officers to move towards the 4th floor in slow "search mode" instead of fast "contact mode".
Some officers began evacuating students from the lower floors to the Rudolfinum across the street, while the search party moved upstairs.
Several of the students present in other 4th floor classrooms fled through windows towards the terrace, then climbed an exterior ledge on the other side of the building and later jumped to a third-floor balcony, sustaining injuries from the fall. Among them was student and athlete Klára Holcová, who slipped from the ledge and fell to her death.
At 15:11 the police officers who were searching for the perpetrator on the third floor were alerted that he was shooting from a rifle towards the streets, with mistaken information that the perpetrator was on the rooftop, while he was actually on 4th floor top terrace. The gunfire also caused panic outside, with crowds fleeing Charles Bridge. Police lost time searching for a route towards the fourth floor and then to the outer terrace, as the area is difficult to navigate. While the first three floors are accessible by the main central staircase, the position of the side staircase leading to the fourth floor was not immediately visible to the officers.
A third-year history student named Tomáš Hercík has been credited with saving lives of several people. At 14:59, one of the students present at a lecture taking place on the 2nd floor received a message about the ongoing killing spree. Hercík immediately raced towards the 4th floor. While passing 3rd floor, he noticed people unassumingly mingling in the corridors. After entering the 4th floor, he immediately heard gunshots and people's cries. While avoiding the perpetrator, Hercík entered numerous classrooms and warned the people inside about the ongoing attack, making sure that they lock the doors, switch off lights and remain quiet. He then retreated to the 3rd floor, where he continued warning attendees in the classrooms until police reached him. As the police officers were unaware of the position of the side staircase leading from the 3rd to 4th floor, he showed them the way. 
At 15:12, the advancing police forces reached the 4th floor and split into two groups, with the first continuing their search for the perpetrator and the second initiating first aid to the victims in the corridor. Authorities reported seeing "piles of ammunition" inside the building's corridors, adding that Kozák had brought multiple weapons into the university. The city emergency services also deployed a large number of ambulance units to the scene.
A video by reporter Jiří Forman showed Kozák on the 4th floor terrace with a