Police said the man who opened fire at an Amish school in Pennsylvania Monday had let the boys and the adult women leave while holding the girls hostage -- and then shot them as police arrived.

Police said they found the bodies of three girls at the scene, along with the body of the gunman, who had turned the gun on himself. They said several other victims were taken to hospitals -- some with very serious injuries. All had gunshot wounds.

The shooter, identified as Charles Carl Roberts IV, 32, sent the male students and some adult females out of the West Nickel Mines Amish School, state police Commissioner Jeffrey B. Miller said. He then barricaded himself inside. Miller said Roberts had forced many of the children to line up against the blackboard and that he bound their feet with wire ties and flex cuffs.

"He bound the female students up by the blackboard and apparently executed them," Miller said.

Miller said Roberts was a husband, father of three and milk truck driver from nearby Bart, Pa. His wife said she suspected nothing Monday morning as her husband walked their children to the bus stop about 8:45 a.m. She said she left the house, then came home later to find what appeared to be several suicide notes to her and the children.

When asked about a motive, Miller said Roberts called his wife at 11 a.m., but did not tell her where he was. Roberts said to her during that call that he was acting out to achieve revenge for something that happened 20 years ago. He told her he loved her and he would not be home, but that the notes he left would explain it all. Miller did not elaborate on what the event was that caused him to want revenge 20 years later, but said that it appears he wanted to attack young, female victims -- which is why he chose the school.

"He told her he loved her and that was it," Miller said.

"It's obvious to us that this was a premeditated hostage scenario," Miller said. "I believe, based on what the investigators have so far, he intended not to walk out of there alive, but he also intended to kill innocent victims."

An emergency call came in from a school teacher, saying a man entered the school and had taken hostages, Miller said. He said there were about 15 male children attending school and somewhere from 10 to 12 female students in the school -- along with teacher's aides and a teacher.

Miller said the shooter allowed all the boys and one adult pregnant female to leave. He then allowed three other adult females with infant children to leave, Miller said. The teacher got out at that time and got to a phone and dialed 911.

There were seven injured victims taken to hospitals, all suffering from gunshot wounds. One of the shot females died in the arms of a state trooper, Miller said.

"He apparently told the kids to line up, " Miller said. "He began to tie the female children's feet together."

"These victims were shot execution-style in the head," Miller said.

Police said Roberts entered the school with the intention of taking hostages. He had two guns, Miller said.

Miller said Roberts was apparently preparing for a long siege, arming himself with a 9mm semiautomatic pistol, a 12-gauge shotgun and a rifle, along with a bag of about 600 rounds of ammunition, two cans of smokeless powder, two knives and a stun gun on his belt. He also had rolls of tape, various tools and a change of clothes.

Troopers responded at 10:45 a.m. and began to set up a perimeter around the school house. The gunman could see the police, Miller said. Police immediately tried to get a hold of the man over a speaker system. A short time later, a call was received from the 911 facility. The 911 operator said he'd spoken to the gunman and that if police did not leave in 10 seconds, he would begin shooting people, Miller said.

The negotiator for police immediately tried to call the man's cell phone, police said. The trooper, who was the negotiator, heard multiple shots in quick succession. It appeared that the gunman was using his automatic handgun, although he had an automatic handgun and a shotgun, Miller said.

The troopers immediately stormed the one -room schoolhouse, but all of the doors were blocked. He had taken boards with him to block all the exits to the building. They couldn't get in through the doors, so they had to break into the windows. By the time they were in, Roberts had shot students, someone who appeared to be a teacher's aide and himself.

Miller said he had no immediate evidence that the victims were sexually assaulted.

Killed were two students, and a female teacher's aide who was 15 or 16 years old, authorities said.

Some two hours after the shooting, about three dozen people in traditional Amish clothing, including hats and bonnets, were seen standing near the small school building, talking to one another and to authorities.

"This is a horrendous, horrific incident for the Amish community. They're solid citizens in the community. They're good people. They don't deserve ... no one deserves this," Miller said.

Roberts was not Amish and appeared to have nothing against the Amish community, Miller said. Instead, Miller said, he apparently picked the school because it was close by, there were girls there, and it had little or no security.

Amish families waited at a nearby farm to find out which children survived. People who were at the scene said that Lancaster County, Pa., has never seen a tragedy like this.

"They're all little kids," said a man who lives near the school. "I see the kids come right by my house … they're always friendly, waving, smile. They come to our house sometimes selling different goods … They're sweet kids. It just blows my mind. It's as quiet as can be out here."

The schoolhouse serves about 30 students from first to eighth grade.

The school is among farmlands just outside Nickel Mines, a tiny village about 55 miles west of Philadelphia.

Statement From Wife Of Charles Carl Roberts IV

The following statement is from Marie Roberts, the wife of Charles Carl Roberts IV, the 32-year-old man accused of shooting students at an Amish school. It was read by family spokesman Dwight LeFever:

"The man that did this today was not the Charlie I've been married to for almost 10 years. My husband was loving, supportive and thoughtful - all the things you'd always want and more. He was an exceptional father. He took the kids to soccer practice and games, played ball in the backyard and took our 7-year-old daughter shopping. He never said no when I asked him to change a diaper. Our hearts are broken, our lives shattered and we grieve for the innocent lives that were lost today. Above all, please pray. Pray for the families who lost children today. Please pray for our family and children."