New York (CNN) -- About a half-dozen bikers accused of beating an SUV driver last weekend used their helmets to attack him and kicked his head and body as he lay on the ground, New York police said.
Police said one of the bikers -- Robert Sims -- also stomped on the driver's head and body, according to a detective's criminal complaint.
Sims was one of two bikers who turned himself in to authorities on Friday. He has been charged with attempted assault, gang assault and criminal possession of a weapon.
According to police, Sims can be seen in a video going after the SUV.
The driver of the SUV suffered two black eyes and cuts on his face and side, requiring stitches, the criminal complaint said.
One of the bikers, Edwin Mieses, was critically injured in the melee. His wife said he is paralyzed.
The other biker who turned himself in, Reginald Chance, is also suspected in the beating of driver Alexian Lien. Police identified the 37-year-old Chance as the man seen in the video pounding his shiny helmet against the SUV.
Chance appeared for arraignment Sunday and was charged with first-degree assault and gang assault, both felonies; unlawful imprisonment; criminal possession of a weapon and criminal mischief, according to court papers. His bail was set at $75,000 cash or $100,000 if secured by property, and his next court appearance was set for October 11.
Chance's lawyer, Gregory Watts, said his client didn't take part in the beating. He said Chance and Mieses are also victims in the case, and he urged prosecutors to call a grand jury to investigate Lien.
"We concede the criminal mischief," Watts said. "It's obvious that he overreacted. But the law does permit someone who is a victim of an accident to at least attempt to get the identification of the motorist. My client obviously overreacted in that manner, but he is not this thug assaulting someone who's harmless, contrary to the public opinion that's being put out there."
Lien was in his Range Rover on his way back from an outing to celebrate his wedding anniversary with his wife and their 2-year-old daughter.
Dozens of bikers swarmed past him on Manhattan's West Side Highway. A cycle quickly slowed down in front of Lien, who bumped its rear tire, slightly injuring rider Christopher Cruz.
Lien pulled to a stop, and angry bikers surrounded his vehicle, hitting it and spiking its tires, police said.
Lien stepped on the gas, plowing into three more bikers, including Mieses, who was critically injured.
One of the bikers, wearing a helmet camera caught the dust-up on video, which later in an edited version appeared on the Internet. It showed the Range Rover stopping at a later point with the biker gang still in pursuit.
A man, who police say was Sims, got off his motorcycle and opened Lien's door, police spokesman Sgt. Carlos Nieves said Friday.
Lien drove off with his door slightly open, but further down the road, traffic backed up, cutting off his path, and allowing the motorcyclists to corner him. A biker, who police identify as Chance, smashed the driver's side window with his helmet.
That's where the video ended.
Afterward, some of the bikers dragged Lien from the vehicle and beat him, police said. His wife and daughter were unharmed.
Cop among the bikers
An off-duty New York police officer was riding with the bikers Sunday and saw much of the confrontation that ended with five injured. But he didn't step in, an official said.
He also didn't tell his superiors about what happened until Wednesday, the source said. The officer, who works undercover, is a member of the motorcycle club.
He may not have been legally obligated to immediately intervene, according to the same source.
It's not clear why he waited so long to report what he saw. He has hired a lawyer and is being investigated by the New York Police Department's internal affairs unit.
Police seized the helmet-cam video and questioned the motorcyclist who shot it.
They arrested Cruz, 28, the biker who abruptly slowed in front of the Range Rover. He is charged with misdemeanors including reckless driving. Cruz was later released after posting $1,500 cash bail and a $15,000 insurance bond. His license was suspended, and he was ordered to surrender his passport.
Cruz's lawyer insisted he is not guilty.
"His motorcycle was struck, and he stood right there," his attorney H. Benjamin Perez said. "He never assaulted this man. He never tried to assault him in any way. And he does not know any of the other motorcyclists who were involved in this beating."
A second biker, who was in custody, was released Wednesday, when authorities determined that he may have been trying to help.
The NYPD released photos Sunday of two other men they want to find and question as part of the investigation and asked for the public's help in identifying them.
Mieses' family, meanwhile, says he is the real victim. "All of his ribs are fractured. His lungs are so badly bruised that he's still on a ventilator," Yolanda Santiago, his mother, told CNN affiliate WCBS.
Mieses' wife, Dayana, told CNN affiliate WBZ that he got off his bike to help the SUV driver. She blamed Lien. "He got scared; he peeled off, and he paralyzed my husband on the way," she said.
'We could not have done anything differently'
Lien was treated at a hospital for slashes to his face.
"My husband was forced under the circumstances to take the actions that he did in order to protect the lives of our entire family," his wife said.
"We know in our hearts that we could not have done anything differently, and we believe that anyone faced with this sort of grave danger would have taken the same course of action in order to protect their family."
It was Lien's wife who made the last of three 911 calls the family placed during the incident.
Bikers have called for Lien to be charged.
"That wasn't fear, that was aggression -- he ran over three bikes," a man who identified himself as Jose told reporters Thursday night. "Are we saying, if you feel nervous you can kill somebody? You can paralyze somebody? I think we need to charge him immediately."
Angry netizens have turned on the bikers, casting them in a bad light.
One biker called for cool heads to prevail.
"We are not here to blame anyone, we are not here to point any fingers," Albert Elkerson said. "The true question is how could we have avoided what happened last Sunday, and what can we do to prevent that."
CNN's Susan Candiotti reported from New York; CNN's Tom Watkins and Greg Botelho reported and wrote from Atlanta. CNN's AnneClaire Stapleton, Lateef Mungin, Pamela Brown, Kevin Conlon and Marina Carver contributed to this report.