bristol, virginia. when he arrives on scene with his dashcam rolling, flames are visible on the right side of the undercarriage. >> i noticed the operator of the truck was standing about 30 feet to the right of the tanker. i ran up to him and asked him what was he hauling? he said it was empty. i said, what was it hauling? he said that it's a gas tanker. and at that point, i knew that the situation got worse because i know that an empty gas tanker is more dangerous than a full gas tanker. >> even though the tank is empty, gasoline vapor remains inside. gasoline is flammable, but the vapors are even more likely to explode. >> i asked the operator whether or not he could separate his cab from the tanker and he said he tried but he couldn't. can you separate it? >> no way. i cannot. >> fearing for their lives, trooper lauer and the driver take cover behind the police