Call for Navy security review

President Obama and the First Lady are expected to attend a memorial service for victims of the Washington Yard shooting on Monday, according to Washington Post reporter David Nakamura.

Read: Call for Navy security review

The US Navy has ordered three new reviews of its security clearances to "better understand the circumstances" under which a gunman killed 12 people at the Washington Navy Yard on Monday.

US politicians are calling for a review into how the suspected gunman in Monday's rampage at the Washington Navy Yard received and maintained a security clearance, despite a history of violent episodes.

Lawmakers say this most recent incident shows serious flaws in the federal government's process for issuing security clearances and vetting contractors - an issue laid bare earlier this year by former National Security Agency contractor turned whistle-blower Edward Snowden.

Democratic Senators Claire McCaskill and Jon Tester plan to send a letter to the Office of Personnel Management's inspector general, demanding answers about how Alexis' background check was conducted for his security clearance.

Aaron Alexis, the 34-year-old man responsible for killing 12 people at a Navy base in Washington yesterday, was a heavy drinker with a grudge against the Navy, The Times reports.

Mr Alexis was also a recent convert to Buddhism, and attended a temple in Fort Worth.

Ty Thairintr, who attended temple with him, said he was upset with the Navy because "he thought he never got a promotion because of the colour of his skin. He hated his commander."

Read: Gunman 'bought shotgun legally in Virginia'

The firm that hired Aaron Alexis said they did two background checks on the suspected Washington gunman, which revealed no issues other than one minor traffic violation.

IT company The Experts said it twice confirmed Alexis's security clearance with the US Defence Department.

The FBI said the weapon used in yesterday's mass shooting at a Navy base in Washington DC was bough legally, in Virginia. A spokeswoman said:

An FBI spokeswoman said they believe Mr Alexis entered the complex with a shotgun, and then gained access to handgun once inside the Navy base. A spokeswoman said:

Read: FBI say deceased Washington gunman acted alone

The FBI have confirmed that Aaron Alexis, the gunman responsible for killing 12 people at the US Navy base in Washington DC, acted alone. A FBI spokeswoman said:

"We believe at this time that the deceased shooter, Aaron Alexis, acted alone. As such with no other suspects at large, the investigation has moved into a stage of evidence retrieval."

Police in Washington have released the names of all 12 victims killed in Monday's Navy base shooting:

• Michael Arnold, 59
• Martin Bodrog, 54
• Arthur Daniels, 51
• Sylvia Frasier, 53
• Kathy Gaarde, 62
• John Roger Johnson, 73
• Frank Kohler, 50
• Mary Francis Knight, 51
• Kenneth Bernard Proctor, 46
• Vishnu Pandit, 61
• Gerald L. Read, 58
• Richard Michael Ridgell, 52