"Tower" is about the 1966 mass shooting at the University of Texas at Austin. Charles Whitman took a position on the observation deck of the main building tower, killing 16 people and injuring many others. He was only the second mass murderer in the U.S. to get into double digits, and exceeded the body count of his 1949 predecessor Howard Unruh.
The movie mentioned Whitman's name only once, concentrating instead on the experience of those on the ground around the tower that day. And it does this through animation, specifically rotoscoping. This seems to have been a happy accident (if anything about this movie can be called "happy"): the director was planning on using re-enactments, but couldn't afford it and went for rotoscoping instead. What this does is hide details: their hair, the fashions that were in vogue at the time, and make these people from 1966 just ... people. Like us. If we saw the details, we'd be thinking about how different those people were from us. As Scott McCloud pointed out in Understanding Comics (the greatest book ever written about comics), it's far easier to identify with a generic, undetailed face. With the rotoscoping, we are them.
This is the story of the survivors, and the people who did heroic things in that horrible time. It's not a movie I'd choose to watch again, but it's a very good movie that I'm glad I watched once.