. >> the fire department also responds, but battalion chief rick pavick doesn't see the vapor cloud.e's taken completely by surprise when the gas finds an ignition source and erupts 500 feet away. >> it was real crazy. it was amazing, is what it was, just to be that close to something that large and watch it spread out. >> when the gas ignites, officer mcadams' dash cam records the initial sound, but the explosion is out of view. the police dispatcher has a clear view of the train tracks and radios officer mcadams. >> we just had a huge explosion. we've got massive fire out here. >> as officer mcadams starts backing up, the flames race down the track and into the camera's view. as the gas explodes over and over again. >> anywhere that vapor from the chemicals had gone just burned, whether it was on the ground, in the air. just nothing but a ball of fire and like a big fuse, it just kept going further and further. >> it was a big mushroom shaped fireball. it went up in the middle and then kind of cascaded down. >> you might want to back your units up. >> didn't have time to really get