There was the Clackamas Mall shooting a week or two ago stopped when a dad pulled his weapon and the shooter saw it and ran, then killed himself.
Many years ago (7?) there was a guy that did the same thing at a mall in Tacoma, Washington. Except he pointed his gun and told the shooter to stop, the shooter shot him (is now paralyzed) and then ran off and hid and killed himself. (Like I tell my kids - never be talking when you should be shooting!)
When you have to shoot...Shoot! Don't talk...
(Line in The Good, The Bad, and the Ugly)