Working on an anonymous tip, authorities located a loaded semi-automatic weapon at Challenge Charter Academy Monday afternoon. According to Newton County Sheriff’s Office Public Information Officer Lt. Tyrone Oliver, an anonymous call came in around 12 p.m. Monday. The caller said that someone had brought a gun to the school.After arriving at the school, authorities spoke with several people and were able to locate the loaded .25 caliber semi-automatic handgun inside an unattended book bag.