MILFORD, Pa. --  For nearly three years, Eric Frein's parents had been silent. They did not speak publicly after their son gunned down two troopers, led hundreds of police on a 48-day manhunt, or even as a jury convicted him of murder last week.

On Monday, they broke that silence, trying to save him from death row.

Debbie and Eugene "Michael" Frein testified about their own failings as parents, rough patches in their marriage, and their struggle to help their son with learning disabilities. Frein's father, jurors were told, was argumentative, sometimes drank too much, and lied to his family about being a sniper in Vietnam -- a fabrication that fueled his son's obsession with guns and the military.

His mother knew her son was a loner who couldn't read until sixth grade. She doesn't know how he became a murderer, but insisted he must have become delusional.

"He's a sweet, kind, gentle person," Debbie Frein testified, sobbing. "I don't know what happened. No sane person would do what he did."

A jury convicted Frein last week of murder, terrorism, and other charges for killing Cpl. Bryon Dickson, wounding Trooper Alex Douglass, and hiding in the Poconos woods for weeks before he was captured in October 2014.

The same group of jurors from Chester County is being asked to determine whether Frein, 33, of Canadensis, should be sentenced to death or life in prison. His lawyers spent Monday presenting mitigating factors they hope will spare his life – none as central as his dysfunctional home life.

A retired Army major, his father was tough, opinionated, and yelled a lot, witnesses said. He did not like police, thought government was too big and that Americans were losing their rights daily -- stances that his son later adopted as his own, and seemed to help fuel his attack.

Frein's best friend from high school, Warren Ahern, said he would avoid Frein's father. He did not like hearing Michael Frein's war stories and tips on outdoor survival, he said. And he did not like that he frequently yelled at his son.

"I've been there when he's been very heavily ridiculed by his father," Ahern, a Silicon Valley software engineer, told jurors.

Michael Frein's "self-aggrandized, narcissistic behavior" made Frein worship his father as a military hero, defense lawyer Michael Weinstein said during the hearing. But it wasn't until after Frein's arrest that the family learned his stories of Vietnam combat were a lie.

Pike County District Attorney Ray Tonkin suggested the testimony was part of a calculated attempt by the defense to shift some blame – enough to mitigate Frein's behavior – onto his parents. He read aloud an excerpt from a prison phone call where the elder Frein told his son the defense argument would be: "It's not your fault, your father's a nut job."

But on the witness stand, Michael Frein expressed regret over his parenting.

"I failed him as a father," he said.

Frein himself has been so distraught since his conviction that he has not slept and is on suicide watch at the Pike County jail, his lawyer said. He had to be brought into court in a wheelchair, would not speak to his lawyers, and appeared dazed. But he appeared alert when his mother took the witness stand, and wiped tears from his eyes as she said: "I love him with all my heart."

Debbie Frein said Eric, the middle of three children, was a quiet boy who struggled in school. Teachers and learning disability experts could not pinpoint a diagnosis for his problems, so she read to him nightly and worked on spelling at home until sixth grade, when he finally learned to read.

"Things that were really easy, Eric couldn't accomplish, and things that were hard, Eric was accomplishing," Debbie Frein said. "Eric can do calculus, but he cannot do times tables."

Debbie Frein said she had rough patches in her marriage of 42 years -- her husband became depressed when they lived in Indiana with their two young sons, and began drinking too much around the time Eric was in high school.

Knowing how much he had struggled through high school, Debbie Frein said, she urged her husband not to push Eric to attend college immediately. He stayed at home, worked, and eventually began classes at East Stroudsburg. His parents also allowed his girlfriend at the time to live in the house with him for a few years.

Michael Frein said he wrote him a check each semester to cover tuition, and gave it directly to his son. Only later did his parents realize Frein never graduated, but instead pocketed the tuition money. And he lied about getting a job.

The week before the shooting, Debbie Frein said, her son said he would not be home the following weekend because he was going to a bluegrass festival in Virginia with friends. Instead, he plotted the ambush and began the odyssey that paralyzed the Poconos.

Life since then, she said, has been "like we're living in hell."

This article contains information from the Associated Press.