Shawn A. Johnson shot Alexander Melcher six times during a random encounter at a Delaware County rest stop Oct. 2, then fled from police in a harrowing, high-speed chase. But after the car driven by Johnson careened off a semi and slid into the median along Interstate 71 in Richland County, authorities took more than two hours to determine that Johnson, 25, was dead.adcelannotate = {"mobilepaywallcategory" : "MOBILE_PREM-LOCAL","nativepaywallcategory" : "NATIVE_PREM-LOCAL"};