Double Tap (1997)

A master assassin who specializes in shooting his victims twice in the head, a "double tap", may not be everything he initially seems to be. An undercover officer ends up teaming up with him after she is not killed in one of his hits on a drug lord and after she determines he is an ex-officer out to kill only those who stand outside the law and are deserving of being murdered. Her investigations lead to dirty officers and uncertainty about whom she can trust.