Based on the information I have seen, and with the provision it could be in error, Baldwin was apparently handling his revolver negligently, and someone somewhere in the supply chain mixed live ammo into the blanks for the set. Baldwin isn't responsible for the latter, but he is responsible for the former if that is what happened. Check this out for an in-depth video exploration of the topic.
What do you mean by, "Maybe the Americans could be a little more responsible with their gun laws"? People who offer opinions about the lax laws usually don't understand what the laws even really are here in the first place. Sure, some vary from state to state, but there are also very real federal laws which apply nationally. What laws do you think are needed, and how do those laws actually solve problems?