SAN DIEGO -- A 28-year-old man was hospitalized Wednesday in grave condition with a head injury he suffered in a late-night Oak Park-area shooting that also wounded his 20-year-old companion, authorities said.

The men, whose names were not immediately released, were standing outside an apartment building in the 3600 block of College Avenue with several other friends when gunfire rang out shortly before 11 p.m. Tuesday, according to the San Diego Police Department.

Officers arrived to find the older victim lying in a parking area at the complex, SDPD Sgt. William Stetson said. Medics took him to a Hillcrest hospital, where he was placed on life support. He was not expected to survive, Stetson said.

A short time later, the younger victim walked into another trauma center, where he was treated for a superficial wound and released.

Detectives have identified no suspects or motive in the case, and are unsure if the assault was carried out by a single assailant or multiple shooters, according to Stetson.

Officers detained but did not arrest a man armed with a pistol who stopped near the site of the shooting shortly after it occurred, SDPD Sgt. Alan Hayward said.

Doctors plan to keep the critically wounded victim on life-support equipment long enough for his family to say their farewells, Hayward added.