Did the drop tank hit you directly? I didn't know you could die from one, due to the fact that you can drop them while on the runway and have the 'explosion' but it does no damage to your plane.
Can't it happen in FSO? I remember folks saying, "Make sure no one is under you when you ditch your tank".
Maybe if you dropped one on someone in the MA, killshooter activates (if it actually does something) and, well, yeah.