The attacker's brother just spoke to the Daily Mail:
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"He was just a guy. Something happened, he snapped or something.
Speaking from his home in Orlando, Florida, Eric said: "We know absolutely nothing, this is just, we are dumbfounded."
"We have absolutely no idea. Our condolences go to the victims and all their families."
Eric said that he and Stephen, 64, lived on different coasts - Stephen's last address was in Mesquite, Nevada - and that they did not speak that often.
He said that his mother was 'in shock' and struggling to cope with the news. He said: "Our family is OK, we're sitting in here in our house hoping that everyone doesn't attack us."
"My mother is 90 years old, lives down the street from me, we're just completely dumbfounded. You can imagine how this is affected her."