A cop was killed this morning after his cruiser smashed into the back of a vehicle on the Kosciuszko Bridge.

The Brooklyn North Homicide detective had been driving back to work from his Suffolk County home – only five hours after finishing his last shift, police sources said.

Cops said the man, who was driving an unmarked police department vehicle, was halfway across the bridge at 6 a.m. when it collided with the other vehicle. Nobody else was injured.

Sources said he was working the “turnaround shift.” He’d finished a 5 p.m. to 1 a.m. stint, and was driving back into squad’s Williamsburg base to start an 8 a.m. to 4 p.m. shift.