Both men involved in the violent incidents in New Orleans and Las Vegas on New Year's Day were US military veterans.

It's unclear how much of a role their service played in their violence but data out of the US shows there has been an increase in veterans being involved in violent acts or being recruited by extremist groups.

Today, Todd Helmus, an expert on military extremism with the US think tank RAND on what could be behind the rise in violent behaviour in ex-military personnel. 

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Todd Helmus, military extremism expert, RAND