I am the shooter and this is my manifesto:
I love Facebook. I am doing this for Zuckerburg, personally.
Facebook has taught me to embrace my mental illness, and allowed me to connect with somebody to buy my gun illegally.
Then, since I'm a coward, I looked around for somewhere where there would be no other gunned civilians around to defend themselves. I got this idea from communications on Facebook.
I was watching Zuckerburg's famous "I smoke meats" video, when I realized... smoking meats = shooting people, he was talking to me DIRECTLY and ordering me to kill kill kill!
This one's for you, Zucky!!!