It happened around 3:30 p.m. Thursday, Dec. 1 in Yonkers on Tuckahoe Road at the Sprain Brook Parkway overpass.
The sergeant, who was on-duty in an unmarked police vehicle, was traveling westbound on Tuckahoe Road when a BMW sedan traveling eastbound "apparently lost control and crossed into the opposite lanes, striking the sergeant's vehicle, and a Westchester County Bee-Line bus," Yonkers Police said.
The officer was pronounced dead at a local area trauma center after being transported there in critical condition, said police.
The operator of the bus suffered non-life-threatening injuries, and several of the approximately 30 passengers were treated at the scene for apparent minor injuries, according to police.
The identity of the officer has not yet been released.
This is a developing story. Check back to Daily Voice for updates.
Click here to follow Daily Voice Mamaroneck and receive free news updates.