MEMPHIS, Tenn. — Many questions remain about the gunman in the Collierville Kroger shooting, including what gun he used and where he got it. WREG is looking into what happens with the evidence law enforcement collects and what information can they actually get.

Investigators collected the traces of evidence scattered across the scene of Thursday deadly mass shooting. WREG investigators have been digging deeper to find out how evidence is processed and analyzed as gun-related crime continues to climb across Shelby County.

The Tennessee Bureau of Alcohol, Tobacco, Firearms and Explosives plays a big role in that. It’s why they also responded to the scene at Kroger.

Agents will analyze the shooter’s gun, working to find out where it came from and if it was purchased legally. That information will then be handed over to Collierville PD.

ATF agents will also focus on spent shell casings. When fired, they leave a unique pattern, almost like a fingerprint. WREG has learned more departments are equipped with machines that analyze the pattern and upload it to a database run by ATF.

The database will let them know if there are any links to casings in other crimes, so that when a detective processes a crime scene, he or she can bring it back to a property room. He or she can immediately enter those cartridge casings or test fires from a gun and get the results in 24 or 48 hours.

The Collierville Police chief was asked about the shooters gun at Friday’s press conference. He said it’s part of their investigation, and they will release more information in the coming weeks, adding, “Right now, it’s not the time.”