DETROIT -

Federal authorities have charged an ex-convict who they say bought a shotgun used by another man to wound four Detroit police officers.

Elijah Gayden is charged with being a felon in possession of a firearm. It's illegal for an ex-convict to have a gun.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives says in an affidavit filed Tuesday that Lamar Moore opened fire with the gun inside Detroit's 6th Precinct on Sunday.

Court documents don't indicate how Moore obtained the gun. But the ATF says Gayden bought the 20-gauge shotgun for $200 last year. He has a 1995 conviction for dealing cocaine in Elkhart County, Ind.

Gayden appeared in court Tuesday. It wasn't immediately clear if he has an attorney. His next court date is Feb. 9.