The Amish community in grieving after a gunman killed five girls in a school shooting rampage have emphasised the need for forgiveness as detectives continue to investigate the motive for the killings.

Members of the peace-loving Amish community around Nickel Mines in Lancaster County, Pennsylvania, where the shootings took place Monday, said they were sad and disappointed but not angry.

"It's just not the way we think. There is no sense in getting angry," said Henry Fisher, 62, a retired farmer with five grown children and 33 grandchildren who has lived all his life in the town some 60 miles west of Philadelphia.

He said the Amish lifestyle with no cars, television or credit cards, was "a more peaceful life ... to keep the next generation living a more humble life."

He also said he did not expect additional security such as locks on schools because this was a "freak accident".

Fran Beiler, 66, of Nickel Mines, "This community is trusting. They don't expect somebody to just come in the doors and start shooting.

"We want to forgive," he said. "That's the way we were brought up - turn good for evil."

"I think the children that go back to the school will have a difficult time but I think that the church as a whole will be very supportive and I think they can overcome that," one member of the community, Jack Meyer, told Reuters.

Other members told Reuters they believed that Amish elders will reach out to the gunman's family in efforts to help the community heal and move forward.

The Amish community appealed for prayers in the aftermath of the tragedy, as did the wife of the killer, Marie Roberts, who remains in a state of shock over the horrific crime carried out by her husband, Charles Carl Roberts.

Police now believe that Charles Roberts' motive for the killings lay in the loss of his own baby daughter nine years ago, while his confession to his wife over the phone moments before carrying out the shooting that he molested two young members of his family 20 years ago shed further light on his motive.

His suicide note read: "I am filled with so much hate, hate toward myself and hate toward God and unimaginable emptiness."

According to police commissioner Jeffrey Miller, the father of three and delivery truck driver had had "dreams of molesting again".

Among the equipment that Roberts brought into the school with him on the day of the shooting were sexual lubricant and flexible plastic handcuffs, indicating to police that he had intended to molest the girls prior to shooting them 'execution-style'.

A statement released by widow Marie said of her husband: "He was an exceptional father. He took the kids to soccer practice and games, played ball in the backyard and took our seven-year-old daughter shopping. He never said no when I asked him to change a diaper.

"Our hearts are broken, our lives are shattered and we grieve for the innocence and the lives that were lost.

"Above all, please pray for the families who lost children and please pray, too, for our family and children."

The couple were married for 10 years and had three young children.

The victims of the shooting were named yesterday as Naomi Rose Ebersole, 7; Anna Mae Stoltzfus, 12; Marian Fisher, 13; Mary Liz Miller, 8, and her sister Lina Miller, 7.