You’re assuming someone didn’t try to stop him and wound up dead.
Absolutely. There's no way to know.
For those wondering why no one took a shot, or believe someone could've... he was well armed and well armored, there was a gas canister used to provide cover and hundreds of innocents in a panic in a darkened theater.
Excellent point. Unsuccessful valor is rarely noticed.
Another good point. Also, all the stories aren't out. We just now heard today about the young man who saved a woman and her child by pushing them out the door, taking a bullet himself. There may be many other stories like that which haven't been told.