Baldwin wasn't entrusted with the gun safety - his ROLE was to point a gun as a prop and pull the trigger.
They employed someone to ensure the safety of the gun (to ensure that blanks were loaded - I assume also to ensure that idiots weren't plinking with a prop.)
Here is the party who bears primary responsibility for this accident:
https://news.yahoo.com/24-old-head-armorer-alec-122916840.html