First, it is not a "tragedy". Romeo and Juliet is a tragedy. What happened in Aurora was an atrocity.
Second, I am hearing anti-gunners yet again floating one of their eternal question, "Why does anyone need <fill in you favorite evil gun or feature>?
OK, I used to be try and be reasonable with them. I tried to explain why a certain "evil" gun can be a rational choice. Then I figured out they don't want an answer. It was like debunking the Creationists on the old Talk.Origins. No matter how often someone explained it to one, he just backed off for while and came back later with the same line of bullshit
Life to short to waste it on idiots so now, in my dotage, I'm going to just give the short answer: It has nothing to do with "need". It's about what I want and it is none of your fucking business why I want it.
In a sane world, there is no reason why I have to justify my choices to you. I don't have to give you a reason why I use Linux instead of Windows or a Mac. I don't have to explain why I drink Southern Comfort or Jack Daniels nor explain why I don't drink Rum or Tequila. I don't have to justify to you the sex or number of people I sleep with. It is none of your business what kind of guns I own or how many rounds each will fire before reloading.
I hope that is clear enough.