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.