Authorities believe at least two people were injured in a shooting at STEM School Highlands Ranch on Tuesday afternoon, according to the Douglas County Sheriff's Office. A ranking law enforcement source told Denver7 that at least one victim was shot and that one suspect was down. Authorities were looking for two other suspects, the source said. The sheriff's office tweeted about 2:40 p.m. that the incident was an "active and unstable scene" at the STEM school, which is located off South Ridgeline Road and Plaza Drive. Authorities responded to the school about 1:50 p.m. on a report of shots fired,...