A man’s behind bars after going full GTA in Chicago ... stealing an ambulance, plowing into cars, and injuring multiple people ... and the start of the chase was caught on camera!

A patient at Loretto Hospital reportedly ran up to the ambulance parked at the hospital, got into the driver's seat and took off. Check out the video ... the ambulance slams straight into a cop car before driving away ... followed seconds later by gunshots and a swarm of police cruisers with smoking tires in hot pursuit.

Chicago Police later confirmed an officer fired at the suspect, but no one was hit. A paramedic sitting in the passenger seat of the ambulance jumped out of the vehicle a couple blocks away.

Police say 59-year-old Lamont Hill allegedly drove the ambulance head-on into a police vehicle, then

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