The jury heard pleas for mercy from Barreto's wife, Maria Esquilin; his stepchildren; and nine other relatives, who called him a good man who stepped up to raise Esquilin's five children as his own.
Tears also flowed from the families of three teen-gang members whom Barreto was convicted of shooting to death in a late-night standoff after months of fights and threats against his stepson.
"Life for my family is unbearable now," said Linda Soto, mother of Joshua Soto, 14. "There is a void that can never be filled."
Soto was killed when Barreto shot at a Toyota Corolla filled with seven teens idling in an alley behind his Juniata Park home.
"I feel anger toward everyone. I can't sleep," testified Maria Lugo, mother of Donti Lugo, 14, another victim. "I will never forget or forgive what he has done."
Testifying through a Spanish-speaking interpreter, Maria Colon said her son, Javier Orlandi, was an "honor roll student . . . . He was only 14. Why was his life taken at such a young age?"
Barreto apologized to the victims' families, insisting, "I never meant for this to happen."
"Life is precious," Barreto said, looking at the families in the gallery. "Hug your kids. Love your kids. There may come a time when you may never see them again."
The jury also heard emotional speeches by Assistant District Attorney Jude Conroy and McMahon.
Conroy mocked Barreto as "hiding behind" his 10-year-old daughter. He said the jury, through its verdict - three counts of first-degree murder - had already found the aggravating factors warranting a death sentence.
Conroy also criticized McMahon's argument that the teens - cruising around Barreto's house, trying to lure his stepson outside to fight - began the events that led to their deaths.
"Translation? 'They asked for it,' " Conroy said. "That's the most outrageous comment of all."
McMahon argued that Barreto's lack of a significant criminal record - one adult marijuana conviction - and his family's testimony show what happened on Jan. 10, 2012, was "clearly an aberration."
"This man is not the personification of evil that needs to be removed from the planet," McMahon said.