 This morning, Trump posted on his social media account, God alone who prevented the unthinkable from happening, and said it is more important than ever we stand united and show our true character as Americans. The FBI says the 20-year-old shooter had no prior record and had not been on law enforcement's radar. He was armed with a semi-automatic AR-15 rifle, which the ATF is now working to trace. CBS News Special Report. I'm Monica Ricks.