2003 F250 6.0. Drove my truck over 500 miles over the weekend. Got back yesterday morning, went to work, came home no problem. Go out to the truck today, started right up like normal. I was going to pull it forward so it was out of the way while I did something else. Put it into gear, gave it throttle and it died. Tried to start it back up, acted like it had no juice at all. The first time it cranked perfectly. Now it acts like the batteries are dead. I’ve had it hooked to another truck charging the battery, and after about 40 minutes it’s at least turning over fast enough that the engine is TRYING to start, but as soon as I let off the key, it’s done. What could’ve happened between last night and this morning to cause this? I’m at a loss.