A tumultuous childhood, coupled with a history of family violence and other risk factors, damaged Lee Turner Jr. and essentially turned him into a ticking time bomb by the time he fatally shot two CarQuest Auto Parts employees in 2011, a psychologist testified Thursday.

“Lee seems to have been saving it up. Then he just falls off the porch,” psychologist Mark Cunningham, a defense witness, said during the penalty phase of Turner’s capital murder trial.

That final phase of the trial could come to an end Friday. Jurors are hearing testimony about Turner’s background as they will weigh whether Turner should be sentenced to the death penalty or life in prison without parole for the killing of two Baton Rouge employees of the car parts company.

Turner, 25, was convicted Monday on two counts of first-degree murder in the deaths of Edward “Eddie” Gurtner III, who managed the CarQuest on Airline Highway near Siegen Lane, and fellow employee Randy Chaney on March 27, 2011.

The penalty phase began the next day.

Turner’s mother, Melissa Moss, delivered an emotional apology earlier Thursday to the Gurtner and Chaney families seated in state District Judge Richard Anderson’s courtroom and pleaded with the jury to spare her son’s life.

“I’m begging that they don’t kill my child. That’s not him,” Moss said of the double-homicide. “That’s not my son.”

Moss, whose voice rose as she tearfully asked for leniency, testified she has felt for the victims’ families “from day one.”

“I apologize to the families. I swear I do. I can only imagine what y’all are going through. I’m sorry,” she said.

Previously during the penalty phase, Gurtner’s and Chaney’s widows and other members of the families testified how the slayings devastated their lives.

Turner could be heard crying and wiped his eyes with a tissue after his mother said Thursday that she feels helpless.

“Lee, I love you. I love you,” she said.

Later in the day, Cunningham characterized Moss’ dramatic testimony as “lots of thunder and not much rain.” The psychologist pointed out that Moss seemed to evade some questions by complaining that she felt she was being attacked during the trial for not being a good mother.

Moss and Turner’s father, Lee Turner Sr., never married. She was a teenager when the younger Turner was born in 1989. Moss said she and Lee Turner Sr. parted ways one to two years after their son’s birth.

Lee Turner Sr. testified Wednesday and also asked jurors not to condemn his son to death.

Lee Turner Jr. was 21 and had started working for CarQuest just 11 days before he killed Gurtner and Chaney during a robbery of the Airline store.

Cunningham, who said brain development continues until about the age of 25, said the younger Turner was abused physically and emotionally during his childhood and grew up in a culture of family violence. The relationship between Moss and Lee Turner Sr. was turbulent at times, the psychologist said, and Moss later had several boyfriends, some of whom were abusive, as well.

“Childhood is profoundly formative,” Cunningham testified. “Childhood matters.”

The younger Turner also lived with other family members at times, he said.

The Turner family had a history of drug and alcohol abuse, which Cunningham dubbed additional risk factors for future violence.

Hurricane Katrina displaced Turner’s family from New Orleans to the Baton Rouge area in 2005.