The more we learn about Mateen the more disturbed we learn he was--cultural Muslim radicalized on the internet, abusive to 2 wives, gay and/or bi-sexual, nasty personality, and the people he killed were in a club he often attended, so he may have known some of his victims, most of whom were probably Puerto Rican heritage.
The gun was not the problem, and it wasn't an assault weapon, it was a rifle, but that's immaterial. He could have done just as much damage with a handgun, or a fire bomb, or blowing himself up inside the building. People who knew him in high school 15 years ago say he was hateful then. He was a hater. He violated all laws about guns, yet he had been cleared by a security company with a Homeland Security contract and the FBI. To say more laws would have stopped him is just a fantasy. His co-workers had also tried to warn their employer, but due to protections accorded certain groups and fear of being called a bigot, they were ignored. "If you see something, say something," apparently only applies to abandoned luggage in airports.
Do not include yourself or me in your comment "USA society is just as mentally warped as the warped individual." And I say that to conservatives also who cry that we're going to Hell in a hand basket because of Hillary and Obama. That's just a lie people tell themselves that is based on political hysteria. None of Mateen's qualities are mine, and not yours. Straighten your spine and do something nice today in memory of those who have died. And by the way, gun violence is half of what it was in 1994, and gun ownership is double.