The FIRST rule of handling any gun is to always check to see if it's loaded. Even if the person handing it to you tells you it's not, check it for yourself. And if you don't know if it's loaded, always assume that it is and never point it at anything you don't intend to shoot.
I'm confused about the Alec Baldwin situation because if it was someone's job to make sure that any gun is unloaded, that's easy. What gets complicated is if it were loaded with blanks. I don't know what blanks look like and I don't know if they are safe.
Here's a gun very much like the one used on the set. I'll show you how to easily tell if a gun is loaded. But remember, if you can't figure it out, put it down or just don't touch it in the first place.