Not everyone shows their emotions so openly and/or changes them that quickly. If I am pissed at you right now, it probably won't be much different an hour from now. But I might find better things to do by the time I wake up tomorrow.
perhaps, or you could stew on it and be even madder. Not a single one of these mass shootings have been knee jerk, the killers planned it for weeks and months in pretty much every case