Alex was pointing the gun at people. We know that from where the bullet went. Only question is how involved he was in making it shoot. The answer is certainly some, unless the gun was handed to him with the hammer cocked and then somehow went off unintentionally.
Proper gun safety would involve guns always being passed open so the recipient can inspect the load status, and if passed closed, you open it to check for yourself. But I understand that is not 'standard film industry practice.'
