A man was critically injured early Tuesday after being struck by a vehicle while trying to help a motorist on Route 21 in Nutley, police said.

Officers responded around 4 a.m. to a crash on Route 21 south, north of Exit 8, where a male pedestrian had been struck in the left lane.

The man was found in critical condition and transported to University Hospital in Newark for treatment, authorities said.

Officials said the man had stopped on the highway shoulder and was crossing the road to help a driver with a flat tire when he was struck by a passing vehicle.

Police said the driver of the vehicle that struck the man remained at the scene.