A Chicago police officer shot and killed a man Sunday after he tried to run over another officer with his car, officials said. That account was corroborated by the female passenger in the car of Dantwain Betts, 21, who police shot and killed about 1:30 a.m. Sunday in the intersection of West 100th Street and South Lowe Avenue, authorities said. But Betts' family disputes the police account. They said witnesses have told them that Betts hit the officer with his car only after he had been shot. Betts, who was shot a block from his home, was pronounced dead on the scene, said the Cook County medical examiner's office. An autopsy conducted Sunday revealed that Betts died of multiple gunshot wounds, and his death was ruled a homicide. Officers received a tip that Betts, who was a suspect in a carjacking, was in the area of West 100th and South Wallace Street, police spokeswoman Monique Bond said. There, officers found his car and followed Betts to Lowe Avenue, where they parked their unmarked squad car in front of Betts' car. The officers then surrounded his car and identified themselves as police, Bond said. Instead of getting out of the car, Betts "disregarded the officers' command and accelerated the vehicle in reverse, running over the officer in the rear," Bond said.  Betts' sister Robin said the family "believes there is a cover-up going on." Witnesses told the family that Betts drove into reverse onto the sidewalk after he was shot, she said. "He lost control of the car and wound up on the sidewalk," she said. "Afterward, police walked up and shot him multiple times. He has been in trouble with the law before, but misdemeanors, juvenile things. He didn't have a weapon or a knife or gun or anything." Bond said the passenger in Betts' car corroborated the police department's account. [MORE] and [MORE]