Pentagon gunman was 9/11 conspiracy theorist acting alone, say officials - The Guardian

John Patrick Bedell, 36, from California, wrote on the internet about government conspiracies in the 11 September 2001 terrorist attacks, "institutionalised violence of government" and other theories.

The shooting came three weeks after Joseph Stack, a disgruntled software engineer with strong anti-tax leanings, flew his plane into an office of the US tax authority in Texas. Stack and an employee of the IRS were killed. - The Guardian

Pentagon gunman 'had gone off the deep end,' according to friends, writings
Pentagon Gunman Dies; Mystery of Assault Deepens - WSJ
John Patrick Bedell: Did right-wing extremism lead to shooting?‎ Christian Science Monitor