An Ooltewah man who authorities say sold the gun to Jesse Mathews that he used to kill Chattanooga Police Sgt. Tim Chapin in April 2011 has been arrested by federal authorities.
Kevin Dawson is charged with dealing in firearms without a federal firearms license and transfer or possession of a submachine gun.
ATF Agt. Neil Harper said Dawson traded a firearm at a gun show to Mathews, a convicted felon.
Agents interviewed Dawson a short time after the fatal shooting of the officer near a pawn shop in Brainerd, and he said Mathews told him he was not a felon.
An ATF investigator at the time advised Dawson he should seek a federal firearms license "due to his apparent frequent and consistent firearms sales."
Authorities said, despite the warning, Dawson continued selling guns without a license.
An ATF officer working undercover began meeting Dawson at a variety of locations and buying guns from him, an affidavit says.
The undercover officer was told that Dawson frequently went to weekend gun shows. He also said he had guns for sale at his home.
He said he could make up to $600 a week dealing in guns. He said he made $25 to $50 per sale.
Dawson at one point told the undercover officer that if he got caught selling to someone out of state "they would bust my a--."
He told the agent, "You've got SOBs that will set you up in a minute." He said he tries "to feel people out" before he sells them firearms to insure that he is "not being set up."
Dawson said he knew someone with a Thompson submachine gun that was fully automatic. He said it was worth from $3,000 to $4,000. He said he had a buyer in Nashville who purchased numerous guns from him and wanted a Thompson submachine gun.
Authorities said this morning it was arranged that Dawson would meet the undercover officer on Browns Ferry Road. The officer had a Thompson submachine gun with him and showed it to Dawson. Dawson had seven firearms in his trunk that he agreed to trade for the submachine gun.
Dawson said of the submachine gun, "I can do something with it."
The agent transferred the submachine gun from the trunk of his car to the trunk of Dawson's vehicle. Dawson helped the agent carry guns back to his car. Dawson was then taken into custody.
Dawson was taken before Federal Magistrate Court Judge Susan Lee, and he was allowed to be released on bond.
A preliminary hearing is set for June 6 at 4 p.m.