49ers RB Trenton Cannon taken off field in ambulance after scary head injury

San Francisco 49ers running back Trenton Cannon was taken off the field in an ambulance after possibly injuring his head and neck during the opening kickoff return against the Seattle Seahawks. 

Cannon accidentally got hit by the legs of one of his own teammates, bending his neck at an awkward angle after knocking his head on Talanoa Hufanga's thigh. 

It was a scary scene. Cannon went down and stayed on the turf until an ambulance came onto the field. His teammates surrounded the area as Cannon was stabilized on a stretcher. 

One immediate good sign: As he was being loaded in, the camera caught Cannon raising his left arm.

The Niners ruled Cannon out with a concussion soon after, but offered no additional details on his injury. 

The 49ers later announced that Cannon is in stable condition and will remain at the hospital overnight for observation.