Gerald Walpin, a former inspector general for the federal AmeriCorps program who was fired by President Barack Obama over his handling of an investigation into a California mayor and Obama supporter, has died. He was 84.

Walpin was killed Friday morning after being struck by a sport utility vehicle in New York, his son-in-law, Allan Tananbaum, said.

The New York Police Department said Walpin was crossing a street on the Upper East Side when he was struck by the vehicle. He suffered serious head injuries and died at a local hospital. The investigation is ongoing and no arrests had been made by Friday evening, a police spokesman said.

Walpin was fired in 2009 as the inspector general who investigates AmeriCorps and other national service programs following an investigation into Sacramento Mayor Kevin Johnson and his nonprofit group, which received hundreds of thousands of dollars in federal grants from the corporation that runs AmeriCorps.

Walpin's probe found Johnson used AmeriCorps grants to pay volunteers to engage in school-board political activities and run personal errands for Johnson. Johnson, a former all-star point guard who played for the Cleveland Cavaliers and the Phoenix Suns, had supported Obama during his first campaign.

Walpin referred the matter to the local U.S. attorney's office, which said Walpin's conclusions seemed overstated and didn't accurately reflect all the information gathered in the investigation. The U.S. attorney's office later reached a settlement in the case.

Obama said he removed Walpin from his position after he lost confidence in him.

Walpin was sworn into office in 2007 after being nominated by then-President George W. Bush. Walpin graduated from College of the City of New York in 1952 and received a law degree in 1955 from Yale Law School. He was a partner with the New York City law firm Katten Muchin and Rosenman LLP for more than 40 years