Somebody who waits until 3 am to pick fights with people they had all day and night to fight.
He/she was a coward, he/she would fight people who were asleep, drunk, or high on drugs (or heavily medicated).
She was a coward, she waited until 3 am to cut that dude's head off while he was passed out from Friday night, claiming it was because he was abusive without ever telling anyone what she was really hiding.