Sean Conroy, 36, found himself cornered and alone on the subway platform near City Hall in March of last year.
He died as Ameer Best, 18, and 17-year-olds Nashir Fisher and Kinta Stanton joined two others in beating the Starbucks manager after they decided to cut school, prosecutors say.
The group's laughter during the attack drew the attention of a police officer who nabbed Stanton. The others were arrested over the next few days. The midday assault was one in a string of subway attacks that chilled commuters.
Thursday, Conroy's mother addressed the teenagers before they were sentenced to 12½ to 25 years in prison.
"I wake up to the sounds of his pleas for mercy while you laughed," Sharon Conroy of Lansdowne said. "I don't understand how you could laugh. You laughed right up to the time of the verdict."
She said her son was her only child. "He was my heart, my soul," she said, her face lined with grief.
At trial earlier this year, Best and Fisher were convicted of third-degree murder and conspiracy to commit murder. Stanton was convicted of involuntary manslaughter and the conspiracy charge.
Stanton had been granted a juvenile-court transfer that would have cut his prison time, but the transfer was revoked when he allegedly shot a friend while on house arrest.
In sentencing the three Thursday, Common Pleas Judge Jeffrey P. Minehart said the five- to 10-year minimum was "not enough time." He said the crime occurred because no one wanted to be the "punk" who refused the dare.
Fisher apologized to the Conroy family and said he hoped to become a lawyer.
"This situation changed my whole way of thinking about life," he told the judge. "Most people (in prison) don't got families, like we do."
The families of the three described the teenagers as "homebodies" who avoided the street.
The other two co-defendants have pleaded guilty and are awaiting sentencing.
Sean Conroy volunteered as an after-school mentor in North Philadelphia and took part in food drives, fundraisers and other charitable efforts. He received several posthumous awards and a learning center at a shelter was named after him, his mother said.
His fiancee and his father, Stephen Conroy of West Chester, also attended the sentencing.