A 20-year-old driving the wrong way on a Westchester, N.Y., highway struck and killed an off-duty NYPD detective on early Friday.

Detective Paul Duncan, 46, died at the scene after his SUV was hit by a car headed the wrong way, a law enforcement source told NBC News. The driver, who had marijuana in his car, has been placed in a medically induced coma after being taken to Westchester Medical Center.

Just before 4 a.m. on Friday, the 46-year-old was headed south in a 2011 Honda Pilot to visit relatives when a 2013 Honda Civic that was speeding the wrong way crashed into him on the Sprain Brook Parkway near the Heatherdell Road overpass in Greenburgh, police said.

The two vehicles collided near a curve in the highway that prevented the detective from seeing far ahead.

"There wasn't much warning about what he was about to encounter," a police source said.

Following the accident, Duncan died at the scene while 20-year-old Efren Moreano of Yonkers was hospitalized in Valhalla, where he was placed in a medically induced coma and listed in stable condition, the New York Daily News reported.

Investigators believe booze might have contributed to the crash, a police source said, adding that damage to Duncan's vehicle indicates that he tried to swerve out of the way at the last moment.

The state police and Department of Transportation should look into ways to improve infrastructure on the highway, Greenburgh Town Supervisor said.

Duncan had joined the NYPD in 1998 and worked for the Internal Affairs Bureau. He lived in Hartsdale with his wife and teenage daughter.

Meanwhile, the crash remains under investigation.