After Bauer's killing, the original owner of the 9 mm Glock handgun watched news coverage of the mournful police procession that carried Bauer's body to the morgue. On Feb. 14, ATF agents knocked on his door with the news that the same gun had been used in a high-profile incident in Chicago — a reference he later realized was to Bauer's killing. It was difficult to fathom, he said, that the gun he'd sold to a fellow member of his shooting club in 2015 wound up causing such a horrific and violent act in Chicago a few years later.