A dapper killer shot an ex-con to death yesterday morning in the doorway of the victim’s Staten Island home, cops said.

The shooter, in a gray suit and tie, knocked on the door of Shaun Adorno’s Heaney Avenue home at 8 a.m. and claimed his vehicle had struck Adorno’s parked car.

When Adorno, 31, opened the door, the killer shot him three times.

Adorno’s girlfriend and their young child were home but not hurt.

The victim, who had served time on weapons, assault and drug charges, died at Richmond University Hospital.

The shooter is described as Hispanic, 5-foot-10 and in his late 20s or early 30s.