(CNN) — Authorities believe at least two people have been injured in a shooting Friday at Arapahoe High School in Centennial, Colorado, Sheriff Grayson Robinson told CNN affiliate KMGH.
The shooter is still believed to be inside the school, Robinson said.
Emergency personnel are advising parents to go to King Soopers, a grocery store in the vicinity of the school, to pick up their children, CNN affiliate KDVR reported.
The high school, with a student population of 2,229 students, has 70 classrooms. The school, which was built in 1964, is part of the Littleton Public Schools system.
All schools in the system have been put on lock down, authorities said.
CNN’s Chelsea J. Carter and Melanie Whitley contributed to this report.