A suburban St. Louis police officer was in critical condition late Friday after he was shot in the neck in what investigators described as an “ambush” following a traffic stop.

Ballwin Police Chief Kevin Scott said the unidentified officer was walking to his car after the initial conversation with the motorist he stopped for speeding Friday morning when that driver “advanced quickly” on him from behind, firing at least three shots.

The officer “had no chance at all” to pull his handgun and “was completely helpless,” Scott said, noting the encounter was recorded by the police car’s dashcam.

“Make no mistake: We believe during this investigation that Ballwin officer was ambushed, period,” St. Louis County Police Chief Jon Belmar said.