DENVER—A police officer who was one of three people killed in a shooting at a suburban Denver shopping district was a school resource officer with a reputation for taking a compassionate approach with students. Police have not explained what started Monday’s shootout that also killed a suspect and a man they described as a “Samaritan” near a library in historic downtown Arvada that is home to popular shops, restaurants, breweries and other businesses about 7 miles northwest of downtown Denver. Authorities were expected to disclose more information about the shooting sometime Tuesday. They have not made public the identities of the other two people who died. With school out for the summer, officer Gordon Beesley was working on patrol when police said he was hit by gunfire shortly after a report of a suspicious incident that authorities have not described. Beesley worked for the Arvada Police Department for 19 years …