Colin Cassidy underwent emergency surgery and is now on a ventilator and heavily medicated as doctors monitor his brain, according to his mother, Amy Cassidy.
She said the procedure went well but her son suffered a traumatic brain injury with significant swelling and bleeding.
"We're just trying to be positive right now," she said.
Police said Cassidy was riding with three juveniles on Meyer Avenue when 40-year-old Phillip Prince followed them in his vehicle. Witnesses told investigators Prince briefly got out of the SUV to confront Cassidy about allegedly stealing the bike before the crash.
According to police, Prince then drove to the bottom of the street, crossed lanes and slammed into Cassidy on the sidewalk. The impact threw Cassidy about 95 feet.
"It's horrible. It's horrible. You don't want to see something like that," resident Kathleen Hogan said. "He was not conscious. He was not moving."
First responders rushed Cassidy to the hospital. Prince was taken into custody at the scene and is facing several charges including attempted murder, aggravated assault by vehicle and homicide by vehicle.
"Even if it was over bike, still doesn't give the guy the right to mow someone down and try to basically kill them," neighbor Geoffrey Brams said.
Cassidy's mother said she is struggling to process what happened as she sits at her son's bedside.
"We're hoping this will only take him a few months of recovery, is our biggest hope, and he can really return to the active, young guy that he was," she said.
She added, "I've already lost one son. To know to go through that and have a grown man target someone else like that, at any age, but let alone someone helpless on a bike, I can't even wrap my mind around it."
Prince was arraigned Monday, and his bail was set at $1 million.
His family declined to comment.