Calcutta, Nov. 6 :    Calcutta, Nov. 6:  An ambulance collided with a Matador van on Vidyasagar Setu on Monday afternoon, killing two persons, including the driver of the ambulance. Deepak Shaw, 25, and his helper succumbed to their injuries at SSKM Hospital late in the evening, police said. The front of the ambulance was smashed after it hit the rear of the Matador, which suddenly switched lanes. Karuna Naskar, a 38-year-old patient of Howrah, her family and the ambulance staff were all seriously injured. Karuna was being taken to SSKM Hospital from Nalpur for emergency treatment. She was accompanied by son Subol and sister-in-law Rekha Naskar. The ambulance, a Maruti van, was speeding along at 80 kmph when the errant Matador van suddenly switched lanes and came in front at the middle of the bridge. 'The Matador was hugging the extreme left lane, but all of a sudden, swerved 70 degrees to the right to come in our way,'' Prabir Santra, who was in the ambulance, said while being treated for severe head and chest injuries at the SSKM. Witnesses said the ambulance spun off its track after colliding against the rear of the Matador and hit the side railing of the bridge, before screeching to a halt. The Matador driver, sensing trouble, stepped on the accelerator and sped away. A couple of NVF volunteers posted on the bridge were witness to the accident. Another Maruti van and a car trailing the ambulance braked in time to avert a ripple collision. The occupants got off and rescued Karuna, Rekha and the others trapped inside the ambulance. D.K. Chandra, an officer of Hastings police station, said: 'I saw the smashed ambulance, but no one could trace the fleeing Matador. A case has been lodged against an unknown vehicle.''