A Pennsylvania police officer faces a homicide charge after investigators concluded she shot a motorist in the back as he lay face down after a traffic stop over an expired inspection sticker.

Authorities accused 36-year-old Hummelstown police officer Lisa Mearkle on Monday of shooting David Kassick twice on Feb. 2 without legal justification.

Charging documents say Mearkle had attempted to pull over Kassick for an expired inspection and emissions stickers before he drove away.

They say Mearkle had caught up to Kassick and had hit him with a stun gun before shooting him near his sister's home.

Dauphin County District Attorney Ed Marsico says Mearkle performed CPR after the shooting.

Mearkle's lawyer didn't immediately return a phone message seeking comment.