The gravity of the fatal attack that Arthur Alston set in motion nearly two years ago had him crying during most of his sentencing hearing yesterday afternoon.

It was Alston who threw the first punch at Sean Patrick Conroy, who was headed to the Center City Starbucks coffee shop that he managed when he was jumped on a subway concourse by Alston and four accomplices.

Conroy, 36, died that day, March 26, 2008, of an asthma attack triggered by the frenzied beating.

Alston and the others, who had cut classes at Simon Gratz High School, had dared each other to attack a stranger.

Yesterday, the 18-year-old man wiped tears from his eyes as Common Pleas Judge Jeffrey Minehart gave him 10 to 20 years for third-degree murder and 2 1/2 to five years for the April aggravated assault of a student at a disciplinary school that he attended while on house arrest.

He choked the boy to the point that he lost consciousness and had to be taken to the hospital.

The consecutive sentences mean that Alston must spend 12 1/2 to 25 years in prison - the same amount of time Minehart gave to three of his co-defendants in October after their trial - Ameer Best, Nashir Fisher and Kinta Stanton.

Alston, waived his right to a trial and pleaded guilty.

"When you're sitting in your new jail cell," Minehart told Alston, "I want you to think about that young man. I want you to think about that fine young man whose life you cut short."

Alston told Conroy's parents and relatives in the courtroom that words could not express how sorry he was.

"I think about what I've done day in and day out. I've asked God for forgiveness. I've asked my family for forgiveness," he said, before blaming his youth for his violent actions.

"I'm not a murderer. I'm not a monster. I'm a kid who made a mistake," added the defendant, who was 16 at the time of the murder.

Sharon Conroy, the victim's mother, had no mercy on the weeping teen, whom she said pleaded guilty only because he was "screwed."

"It rips my heart out every time I see you," she said, after recalling how Alston joked and swaggered with his co-defendants during court hearings.

"Sean grabbed Mr. Alston's leg during the attack and begged him to stop. Instead of stopping, he just laughed in my dying son's face," she said.

"You are a liar, a coward and a murderer," she added.

A fifth co-defendant, Rasheem Bell, who testified for the prosecution during the August trial of Best, Fisher and Stanton, will be sentenced Jan. 4.