This is probably the FO who was let go a few weeks ago who called out sick for a reserve assignment, but didnt realize that he needed to call in sick for the last day of reserve as well. They called him for that last day, he was out of position at home, final straw.

From what I was told, he previously had an "oooops" with an aborted takeoff and was on probation still. Also, the person who had to cover his reserve assignment was Teo in DFW..and he was saying how heads would roll over it.