The suspected gunman in the cold-blooded killing at a Harlem smoke shop was arrested Tuesday, accused of murdering another victim hours earlier and ID’d as having shot at cops two years ago. Messiah Nantwi, 21 — who was last arrested in 2021 for shooting at three Bronx officers, prompting the cops to return fire and gravely wound him — was tracked down through a CrimeStoppers tip and busted for the deadly Sunday encounter inside the smoke shop on Malcolm X Boulevard near West 125th Street, authorities said.