A man accused of driving drunk and causing a fatal wreck should not have been allowed to leave the hospital, the victim's mother told CBS Atlanta.

The suspect remains at large.

But Gwinnett County police on Thursday defended their handling of the case,  saying the suspect only was charged with following too closely at the time he walked out of Gwinnett Medical Center.

"We've never had the manpower to post a guard on a citation," said Cpl. Jake Smith, a Gwinnett police spokesman.

Brayan Rivera, 23, was driving a 1997 Mitsubishi Montero around 3:15 a.m. Dec. 12 when he struck a 1999 Cadillac DeVille on I-85 that had stopped due to an earlier wreck, police said.

A passenger in the DeVille, 22-year-old Joshua Keith, suffered serious injuries and was taken to the hospital. He died about six hours later.

Rivera also was taken to Gwinnett Medical Center, with unspecified injuries.

"When Mr. Keith passed away, they immediately returned [to the hospital] but it was too late, Rivera was already gone," Smith said.

A field sobriety test was not conducted on Rivera because he was injured. Blood tests from the hospital showed he was legally intoxicated, police said.

Police charged Rivera with DUI and first-degree vehicular manslaughter. But they have not found him.

Keith's mother, Demetria Gholston, told CBS Atlanta she is raising money for a reward to help catch Rivera. She expressed outrage he was allowed to check out of the hospital.

"I feel like if things had been done differently, he would be in jail right now," she said. "I am just going to fight until the end until justice is served."

Police post guards at the hospital on a case-by-case basis.

The investigator "notifies the supervisor, and he considers the circumstances and severity and decides whether to post a guard," Smith said.

Rivera, who was carrying a fake driver's license, is about 5 feet 9 inches tall and 180 pounds, and has black hair and brown eyes. He is possibly from Honduras or El Salvador and has worked in construction in the past, police said.

Anyone with information on Rivera's whereabouts should contact the Gwinnett Police Accident Investigation Unit at 770-338-7430, ext. 5670.