When it comes to solving gun crimes, knowing where the weapon came from can make a big difference. A trace of the guns used by a felon to kill three first responders in Burnsville earlier this year, led investigators to that man’s girlfriend. There is only one place in the world where traces like that are done. It’s in West Virginia. WCCO Senior Investigative Reporter Jennifer Mayerle takes us to the ATF National Tracing Center to see how it works, and ask if there’s a better way.