Definition: Given a document, generate a short title of the document. The title should convey the main idea/event/topic about which the document is being written. Note that URLs in the text have been replaced with [Link].
Input: Harrowing video footage taken from inside the high school where suspected shooter Nikolas Cruz opened fire on Wednesday shows distraught students crying and screaming as gunfire rings out.
That’s when police say  19-year-old Nikolas Cruz   equipped with a gas mask  smoke grenades and multiple magazines of ammunition  opened fire with a semi-automatic weapon  killing 17 people and sending hundreds of students fleeing into the streets.
 Nikolas Cruz   19  has been identified as the suspected shooter at the Marjory Stoneman Douglas High School in Parkland  Fla.
Authorities offered no immediate details about  Cruz  or  his  possible motive  except to say that  he  had been kicked out of the high school  which has about 3 000 students.
Students who knew  him  described a volatile teenager whose strange behavior had caused others to end friendships with  him .

Videos capture screaming students during Fla. school shooting