Police have made an arrest in what one detective called the "vicious" and "brutal" beating of a 53-year-old maintenance mechanic who was bicycling home from work during the May 30 "flash mob" attacks on South Street.

Stephen Lyde, 21, was one of eight males who knocked the victim off his bike and "brutally beat him to unconsciousness," leaving him with internal injuries and skull, rib and facial fractures, said Capt. Laurence D. Nodiff, commander of South Detective Division.

They robbed him and left him to "bleed in the street," Nodiff said.

The victim was on life support at Hahnemann University Hospital for days, Nodiff said, and two weeks after the attack, he remains hospitalized in stable condition.

Lyde was charged with aggravated assault, robbery and related offenses. In 2005 he was charged with aggravated assault and robbery, but the charges were dismissed, according to online court records.

Praising the "hard investigative work" of the eight detectives and warrant officers who stood with him yesterday at 1st District Police Headquarters, Nodiff said that police expect to make additional arrests soon.

No severe injuries were reported in initial media accounts of youthful "flash mobs" - numbering in the thousands and organized via cell phones and online social networks - that overran South Street, terrorizing pedestrians and motorists.

A city employee and a taxi driver incurred minor injuries when they were pulled out of their cars and assaulted. About the same time, a swarm of teens looted a convenience store at Broad and Catharine streets, according to video surveillance released days after the near-riot.

But the case of the beaten cyclist - by far the most severe incident - was first brought to public attention this week by Daily News columnist Ronnie Polaneczky, who detailed the man's fight for his life in Hahnemann's intensive care unit after suffering a frontal-lobe injury.

Yesterday, the mother of the man, whom Polaneczky referred to as "John," said that she was pleased about the arrest.

"We feel great that the cops got him and hope they get the rest of them," she said. The police "need to get them off the streets and keep them off the streets.

"You don't want to be a prisoner in your own home while the riff-raff run the streets."

John's close friend, Marcia Houston-Leslie, said: "I am glad. You don't want crime like this to go unpaid for. If people do this to someone, they need to be held accountable for it."

"The police have been very wonderful," John's mother said. "They have called us and been up to see [John] and really been on top of this."

Capt. Nodiff said he hopes this arrest sends a message to those who assaulted people during the May 30 "flash mob" turmoil.

Nodiff said that on South Street last weekend, extra police were deployed and no serious incidents were reported. Again this weekend, he said, police will be out in force continuing to show "zero tolerance" for violence. *

Columnist Ronnie Polaneczky contributed to this report.