NASCAR superstar Tony Stewart drove his race car into another driver Saturday night … sending the man to the hospital where he was later pronounced dead.

Kevin Ward Jr. had gotten out of his car after an on-track accident involving Stewart during a sprint car race (dirt track) in Canandaigua, NY.

Witnesses say Ward appeared angry after the accident and was attempting to point at Stewart as he drove past on the following lap — but Tony ended up hitting him … sending Ward flying down the track.

Hours after the accident, police said they were investigating Ward’s death as an “on-track” incident, and not a criminal matter.

Stewart was  supposed to race Sunday in the Sprint Cup race in Watkins Glen, NY. So far, he’s still planning to do so.