WASHINGTON (AP) -- The FBI says the Washington Navy Yard gunman left behind a note, saying he was driven to carry out the attack by what he believed was constant bombardment with extremely low-frequency radio waves. Authorities say the behavior of Aaron Alexis in the weeks before the shooting, along with records recovered from the hotel room where he was staying, reveal a man who was increasingly controlled by paranoia and delusions. Alexis killed 12 people before being shot and killed by police. The FBI says he wasn't targeting any particular individuals.

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