Actually students were informed first and most parents didn’t find out until somebody posted on the WashU parents FB group. It was kind of an odd situation all around.
The same fraternity was put on suspension for hazing and was supposed to not hold activities but they violated the rules again. The remaining members were moved to on campus housing after the fraternity shut down.
Missouri has fairly lenient gun laws but WashU is pretty strict with their rules. The pistol in the car on-campus in the garage was the big no-no along with the AR-15 off campus.