Yeah, it's the fact that he:
1) Hired the chick he was banging for a position that had nearly 200 applicants.
2) Lied about the situation repeatedly to the AD and other administrators in the days after the accident.
Apparently Arkansas still gave him a chance to stay on with some penalties (pay cuts, suspension etc. I guess) but he refused.
I wouldn't want him anywhere near my school after all that. If it was just an affair, then that would be unfortunate, but not a deal breaker. But with the improper hiring and lies, that's just too much.