CHICAGO (AP) - An AIDS activist and city health department employee was charged with murdering a cabdriver by running him over with his own taxi during an argument.

Michael L. Jackson, 37, was charged Sunday and fired by the city Monday.

Police said witnesses saw Jackson, a passenger, fighting with driver Haroon Paryani, 61, in front of Jackson's apartment Thursday. Police said Paryani fell, and the passenger jumped in the taxi, ran over the cabbie several times and drove off.

Jackson's attorney, Michael Oppenheimer, would not discuss specifics of the case but said, "Once the facts come out, we believe, as does Mr. Jackson, that he will be vindicated."

Jackson was a specialist with the city Department of Public Health's division on sexually transmitted diseases. He was also founder and former president of the Hearts Foundation, which raises money to help AIDS victims.

"This is unbelievable," said the foundation's vice president, Todd Armbruster. "He's such a docile and caring human being. I can't imagine him hurting a flea."