Police on Thursday released the name of the man dropped off at Grady Memorial Hospital with gunshot wounds. But investigators still aren't sure how he got shot and who brought him to the hospital.

The man, identified as Calvin Cooper, was dropped off around 4 a.m. Wednesday, Atlanta police said. On Thursday afternoon, Cooper remained in critical condition, according to Officer Ralph Woolfolk.

A possible witness was seen outside the hospital at the same time the injured man arrived. Police are asking for the public’s help to identify a man, seen wearing pants with what appears to be an American flag on the left leg.

Anyone with information on the shooting or the man’s identity is asked to contact investigators at 404-546-4235 or Crime Stoppers at 404-577-8477.