CHICAGO (CBS) — Chicago Police on the West Side Saturday shot a man whom they allege tried to run down an officer trying to make a drug bust.

Police claim officers saw the man conduct a hand-to-hand drug sale on the corner of Springfield and Chicago Avenues, which Fraternal Order of Police spokesman Pat Camden says has been a problem area for police.

Camden says that when the officers pulled up to the man he took off running. Police say he ran into a nearby alley, jumped into a silver van, locked its doors and gunned the engine.

Police and Camden say the officer ordered the man to halt, get out of the van and put his hands up but he refused and tried to drive off. Two people claiming to be eyewitnesses say the man did not try to evade them and clearly put up his hands.

Police say that the officer jumped onto the bumper of the car and that, as the van moved, he feared for his life and fired through the windshield. The eyewitnesses claim that the van was stationary the whole time and that the officer jumped onto the bumper and fired unprovoked into the car.

Another eyewitness, named Adrienne, said she walked by moments later and saw the man hanging half out of the van. She claims that when he cried for help and asked someone to call an ambulance, the officer allegedly dragged him from the car, threw him to the ground, stomped him with their feet and walked on him.

Chicago Fire Department spokesman Larry Langford said that paramedics transported the 23-year-old man to Mount Sinai Hospital in serious condition. His wounds are not believed to be life-threatening.

Police and Camden said officers at the scene found drugs during a search of the vehicle.

The Independent Police Review Authority is investigating.