Luigi did it, and he really was that stupid.

Given that he was valedictorian at his school, I find that unlikely to be the option.

I think you’re missing a 4th option:

• He did it, and believed it not worth the anxiety/suffering of living the rest of his life as a wanted man, so did what he could to get away from the immediate scene but ultimately turn himself in so to speak.

And there are almost certainly more nuanced options out there.