PHILADELPHIA — One suspect was charged and a second was being sought in the killing of a Philadelphia police officer who was shot with an assault rifle while responding to a bank robbery, police said.

Levon Warner, 38, was charged with murder, robbery, conspiracy and related offenses, Deputy Commissioner William Blackburn said at a news conference Sunday. A second man, Eric Floyd, 33, believed to have escaped from a halfway house in Berks County, is also wanted on a homicide charge. A third man, Howard Cain, 33, was shot to death by police.

Sgt. Stephen Liczbinski, a 12-year veteran who would have turned 40 on Tuesday, was responding to the robbery of a bank inside a grocery store around 11:30 a.m. Saturday. The suspects fled and opened fire after Liczbinski confronted them a short distance away, authorities said.

Blackburn warned that the wanted suspect, Floyd, should be considered "extremely armed and dangerous."