This is video Bladensburg VFD Chief Randy Kuenzli shot yesterday at 38th Street and Rhode Island Avenue in Mt. Rainier, Maryland which is within spitting distance of PGFD Station 855, Bunker Hill. Station 855 was assigned elsewhere and the call was handled by Station 809, Bladensburg VFD. It's engine responded with seven on board and got there after the explosion that blew the roof off the ambulance. I am assuming that is an oxygen tank letting loose.
The explosion occurs at 1:10 in the video. I added a slow-motion version at the end of the video. There are a number of other smaller blasts in the video. Some that you would expect with any vehicle fire.
Thanks to Chief Kuenzli for sharing.