The guy who crashed an 18 wheeler into Tracy Morgan's limo-bus turned himself in Saturday night after being charged with death by auto ... and he's already back out on the street.
35-year old Kevin Roper bonded out hours after being booked.
As we previously reported, Morgan was riding in a limo bus on the NJ Turnpike on his way home from a gig last night ... when it was rear-ended by an 18-wheeler and overturned.
One person died in the crash -- Jimmy Mack McNair, a comic who was a passenger in Tracy's limo.
Morgan is in critical condition but according to one unconfirmed report he's conscious.
A rep for Walmart says Kevin has been suspended pending the police investigation's outcome.