Friends said Burke, a military surgeon at Eisenhower Army Medical Center on Fort Gordon, remains in a coma induced by doctors who performed surgery to relieve swelling in his brain.
Late Sunday he was still in critical condition, according to a Medical College of Georgia spokeswoman.
"It's the first time we've had a confrontation with a car in 30 years," said Brett Ardrey of Outspokin' Bicycles, an Augusta bike shop where cyclists gather several times a week for road rides.
Burke was part of a group of about 15 cyclists who'd gathered Friday at Outspokin' to ride a route that Ardrey said was regularly traveled by cyclists.
A spokesman for the South Carolina Highway Patrol said the cyclists were northbound on Beech Island Avenue about 6:40 p.m. Friday when five of them were struck from behind by a sport utility vehicle driven by 41-year-old Daniel Johnson, who lives at 478 Beech Island Ave.
All the cyclists in the group were wearing helmets and reflective gear, said Lance Cpl. Joseph Robinson.
Johnson, who was not injured, told investigators that he was distracted behind the wheel, leading SCHP to attribute the crash to inattention, Robinson said.
Robinson said a determination on charges will be made later this week.
Also receiving bad scrapes and bruises from the impact were Augusta-area cyclists Laura Farmer, Scott Moore, Judith Speck and Hugh Ray.
Johnson's father, with whom he lives on Beech Island Avenue, said his son and the family were distraught over the accident.
"It's a terrible situation; we don't know what to do or say," said the father, also named Daniel Johnson. "We just keep praying for (Burke) is all we can do."
He questioned why riders chose their road. "Beech Island Avenue is crooks and turns, and it's narrow," he said.