the regional roanoke region airport. flanagan then left the airport in a chevrolet sonic that he had rented earlier in the month. >> reporter: these tweets started around 11:10. around the same time police discovered he switched vehicles. he's posting things to social media while on the run first trying to justify why he went after alison parker and adam ward and then unbelievably posting video he filmed while killing them. what the shooter didn't know is the same phone he was using to post those heinous images is how authorities were tracking his moments and closing in. his car was first spotted here nearly 180 miles away from the airport. >> shortly before 11:30 a.m. this morning virginia state police trooper was on patrol along interstate 66. her license plate reader alerred to a license plate on the chevrolet sonic traveling east on 66. the driver of the sonic refused to stop and sped away from the trooper. it was only a minute or two