WASHINGTON -- US police are still searching for a lone gunman who on Wednesday killed two people and injured four others in northwest Baltimore, about 40 minutes' drive from Washington D.C.

The armed shooter is still at large as he fled on foot from the scene after shooting several men and women standing in front of a convenience store, Baltimore Police spokesman T.J. Smith told a press conference.

Two adult men were shot at multiple times, with one dying at the scene. The second man was taken to the hospital but later died from his injuries, said a CBS report.

Among the injured, one was in critical condition and three others were suffering from non-life-threatening injuries, said the police.

"We believe that this probably an act of retaliatory violence," said Smith.

"This is an area where there were some other crimes recently and we do believe that at this point in time, that this incident is connected, possibly to an earlier incident."