Undated handout photo of Aaron Alexis
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More details about Navy Yard shooter

17 September 2013 Last updated at 23:13 BST

More details have emerged about the man who killed 12 people at a Washington DC Navy installation on Monday.

34-year-old Aaron Alexis was a former US Navy reservist who had a valid pass for the secure site at the Washington Navy Yard as a military contractor.

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

Mark Mardell reports.