Even if he hadn't said he had a bomb, he was acting suspisciously and was told to put the backpack down. He then tried to reach inside of it. I believe they would have had enough reason to shoot him just because of that. How much mobility does a person need to trigger a bomb? I would think not much.

People are so used to second chances, being cut some slack, or being allowed to argue, and there are just some situations where slack can't be afforded. I was in one of these once. When someone has a gun pointed at you, you do what they say, unless you want them to shoot you.

There are numerous contributing factors and places where the end might have been prevented. He could have taken his meds, his wife could have not talked him into flying, the people who allowed him to get on the plane might have noticed something odd, such as a BACKPACK ON HIS CHEST, somebody might have stopped him from running down the aisle, etc. That none of these possibilities occurred ensured he just kept plunging toward a future of getting shot. All the wrong decisions or non-decisions played out until there were just Air Marshals and guns, and they were the ones who had to make the final decisions and get the blame.