Erupt dangerously. Reference to ‘postal’ comes from news accounts in the 1990’s when postal workers brought guns to work and started shooting co-workers. Though going postal doesn’t mean someone  has a gun, it does signify that they are extremely distressed and angry. (Compare to Go Nuclear or Go ballistic.)

“When I asked my dad if I could borrow  his car for my Friday date, he went postal on me because I had crashed my own car and he didn’t think I should ever drive again.“