According to his rep, Dalton -- who also played young Harry in "Dumb and Dumber To" -- was a passenger in his friend's car late Saturday night in L.A. ... when another vehicle t-boned them. Dalton shattered his hip/pelvis and his femur. He also suffered horrific cuts to his face, and some serious eye trauma.
The damage was so bad, doctors had to reconstruct the right side of his face and remove glass from his eye but we're told his vision will recover. Police arrested the alleged drunk driver and as of now, he's currently still in jail.
Gray is the 2nd AHS cast member to be struck by a car in the last few months. Ben Woolf was struck by an SUV while crossing a street in February ... and eventually died from his injuries.