[J-Ri]

You can do a couple quick quick checks before you take it in. Slamming the hood and having it start (or bumping the cable ends when removing the jumper cables) could possibly mean loose battery cables or a broken wire somewhere. Clean the battery cable ends and tighten them up, and with the engine running, wiggle all the wire harnesses you can see. If the engine dies, you have found the general area of the fault.

Loose battery cables will cause the system voltage to drop so suddenly with a load (such as your brake lights, sounds like you were slowing and turning when this happened?) that the alternator can't adjust it's output fast enough and voltage goes below the point where the PCM can function.