New Freedom, Pa. ? Losing her younger son Gregory, murdered in the laundry room of their home almost five years ago, was difficult enough.

But Sue Witman said it was even harder to bear the verdict against her other son, Zachary, who was convicted last week of first-degree murder in his brother’s death after a two-week jury trial.

“At least when they killed Greg, they killed him. As opposed to Zachary, who they’re torturing for doing nothing,” she said Wednesday.

Sue Witman and her husband, Ron, insist that Zachary did not kill his brother. Ron Witman has vowed “to spend the rest of my life trying to find Gregory’s killer.”

Prosecutors did not offer a motive for the killing, which took place shortly after Gregory, 13, arrived home from school. Zachary, then 15, had been home sick that day, and told police he went downstairs after hearing a loud noise and discovered his brother’s body.

Gregory died from more than 100 stab wounds to his head, neck and hands. He had been virtually decapitated.

The murder weapon, a small knife that matched others in a collection in Zachary’s bedroom, was found buried along with a pair of bloody soccer gloves beneath a backyard pine tree. Soil from Zachary’s socks matched dirt in the back yard.

A forensics expert testified that blood on Zachary’s sweat shirt indicated he was near his brother at the time of the murder. All the DNA collected at the scene was linked to Witman family members.

York County Dist. Atty. Stan Rebert said he remained convinced of Zachary’s guilt. He said neighbors should not worry that a murderer is on the loose.

The Witmans “may be justified in their own minds that their son is not the killer, but it’s no basis for resurrecting this ‘mad killer’ myth,” Rebert said.

Zachary lived with his parents under house arrest until the May 21 verdict. Although his sentencing is six weeks away, first-degree murder carries a mandatory sentence of life imprisonment.