I had to point this out – and they may change the link as well, however the BBC article on the shooting refers to one of the killer’s guns as a 22mm.
Police confirmed that two handguns – 9mm and 22mm weapons – were recovered at the scene of the second shooting, and that one of them was also used in the first incident.
Just a note, dear English readers but it’s actually a .22 LR, in which case the “22” is 22/100’s of an inch. In the ol’ metric that would be about a 5.5mm bullet.
The 210 foot Coast Guard cutter I was on had a 25mm cannon mounted on the main deck, somehow I don’t think that the shooter had any anti-shipping hardware in Norris hall with him.