a/c systems are designed so that they don't pump if there's nothing to be pumped
the loud PSHH was the refrigerant leaking out all at once, possibly from an o ring going, but those are set into recesses and don't just blow out
a hard line could have cracked, or a rubber hose could have split, or ****, maybe someone left a fitting loose during an a/c service and it blew apart
check everything, if you have to, pressurize the system with air to find the leak, fix it, then have the system vac'ed and refilled
and oh yea, since it sounds like the a/c system had a rapid depressurization, you might get lucky and find an oil stain near the failure. the one time i had a line fail on me while i was working on a car, it left a oil "halo" on the wall 5 feet behind me ... it definitely makes a mess