Both of these things can be considered griefing. Sitting in a vehicle seat and not doing anything is a known griefing strategy. It has happened to me multiple times on bz2 where someone would sit idle in the amtrack doing nothing. Stealing a vehicle is also considered griefing.
He could have just run to the bathroom to take a violent shid. None of us have any knowledge of undue intent. To assume he is guilty of an infraction and is deserving of punishment is extreme.