As he arrived at the White House's Christmas reception, Trump paid tribute to those killed and injured in the three attacks.

Rhode Island is known to have some of the tougher gun laws in the country, even though the law passed this year banning the sale of assault-style rifles has not yet gone into effect. Regulations on firearms purchases and possession have been added to the law piece by piece over the decades and can be read here.

Rhode Island's Governor Dan McKee has directed flags to be flown at half-staff after a shooting at Brown University left two students dead and nine injured.