A person or persons could take him down by rushing him from behind.
lol - when was the last time you were in a movie theatre?
If he walked in from the bottom corner and started shooting in front those people were dead and the rest hit or scrambling. No one left to tackle him “from behind”
This was a terrorist like attack that little have could have been done to stop.
I am going to be nice. I will not post what I would given your post.
I hope that doesn't make any sense to you.
5.56mm
Nobody was behind him!