By Tom Hals and Brendan O’Brien (Reuters) – Remington Arms will pay $73 million to the families of five children and four adults killed in the Sandy Hook Elementary School massacre, the families said on Tuesday, marking the first time a gunmaker has agreed to a major settlement over a mass shooting in the United States. Twenty students and six adults were killed on Dec. 14, 2012, in Newtown, Connecticut, by gunman Adam Lanza, who used a Remington Bushmaster AR-15 rifle to shoot his way into the Sandy Hook Elementary School after killing his mother at home. Remington Arms will pay $73 million t…