A gunman has shot dead four girls and injured several others before killing himself in an attack on an Amish school in the US state of Pennsylvania.
The gunman entered the class and ordered all the boys and some adults to leave. He then tied up the girls and began shooting them in the head.
Police named the killer as 32-year-old truck driver Charles Carl Roberts IV. He is not Amish himself.
The attack is the third shooting at a US school in the past week.
In the latest shooting, the gunman was said to be heavily armed and seemed prepared for a long siege.
He lined up the girls in front of the blackboard, tying their feet using wire or plastic cuffs.
"It appears that when he began shooting these victims, the victims were shot execution style in the head," said Pennsylvania police commissioner Col Jeffrey Miller.
The attack happened at a one-room school for Amish children aged six to 13 in the village of Paradise near Nickel Mines in Lancaster County.
The Amish are the Anabaptist Christian descendants of German settlers who reject many types of modern technology in their effort to lead a life true to holy scriptures.
They restrict the use of cars, telephones and television to varying degrees.
Col Jeffrey B Miller said the gunman entered Georgetown School in the morning, armed with an automatic handgun and shotgun.
He told the boys to leave, along with a pregnant woman and three women who had young infants with them.
He then tied up the girls and barricaded the doors with large pieces of wood.
Police arrived at the scene at about 1045 (1445 GMT) and set up a cordon around the school, Col Miller said.
The officers tried hailing the gunman on their car loudspeakers, but were unable to make contact, he said.
The Associated Press news agency quotes Col Miller as saying a person who visited the school passed on a warning from the gunman that he would open fire unless the police withdrew.
As the message was going through shots fired in rapid succession were heard, Col Miller said.
Police stormed the building, breaking the windows to enter. But by the time they got there three girls and the gunman were dead. A fourth girl later died in hospital.
Seven people were found injured, at least three of whom were shot in the head.
Roberts was a local milk tanker driver who often picked up milk from Amish farms in the area.
A father of three, he had worked his night shift as usual on Sunday night, finishing at 0300 on Monday.
FACTS ABOUT THE AMISH
Anabaptist Christian denomination
Communities in the US and Canada
Many communities reject links to outside world
Most Amish shun modern technology including electricity and cars
Plain clothing - no buttons allowed in some communities
Speak English and a German dialect called Pennsylvania Dutch
His wife said he had seemed perfectly normal as he walked his children to the school bus at 0845, as he did every day.
However, when his wife returned to the family home around mid-morning she discovered suicide notes that he had written to each of his children.
The police said there were indications that he was motivated by an incident that happened some 20 years ago.
It is not thought that Roberts had anything against the Amish community but chose the school because it was close by and had young girls.
In a separate incident, two Las Vegas schools, one high school and one elementary school, were temporarily locked down while police hunted for a teenager spotted carrying a gun on the high school campus.
These latest incidents come at the end of a week of gun-related violence in US schools.
Last Wednesday a 16-year-old girl died when an armed man, who also killed himself, took six students hostage at a Colorado high school.
And on Friday, a head teacher at a high school in Wisconsin was killed when he confronted an armed 15-year-old student as he entered the school.