There was mention of tannerite, which detonates from firearms round impact. If he taped some to the side of the kero tanks, it could explain it.
I’ve seen other stories that now say there was access to his room even after his car left. What if he did have help, and a key to this is the accomplice took the car loaded with explosives to an area near the tanks. That would be the dry run in the days leading up. However on the night it happened, his accomplice bailed. There was no car to shoot at to explode. Tried to just go ahead and take some shots at the tanks. Realized the gig was up and did as much damage as possible. My gosh my head is spinning with all this.
Please see #86. From that distance he only hit the tanks a few times. With one round penetrating. I think the car was supposed to have been parked near the tanks. A lucky shot might have done the trick.