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Navy Yard: FBI looking at gunman's past

17 September 2013 Last updated at 19:46 BST

The FBI says an investigation is under way to try and examine the past of the gunman who killed 12 people at a US Navy facility on Monday, but would not comment on his medical or criminal history.

The US media have been reporting that Aaron Alexis had received treatment for mental health issues.

Speaking at a news conference, Valerie Parlave also addressed questions about the weapons that Alexis used in the shooting.