Worcester police are investigating how a 34-year-old man who walked into a hospital with multiple stab wounds to the chest received his injuries. Police said that hospital surveillance shows the man being driven to the entrance in a dark-colored sport utility vehicle and then escorted to the hospital’s doors by the driver. The driver left the victim and drove away. The victim, who underwent emergency surgery, was in fair condition Sunday night, police said. The man has not given authorities any details about the stabbing. Worcester police officers later found the SUV that allegedly was used to drop off the victim.