(CNN) -- An active shooter is on campus at the University of Oklahoma in the city of Norman, the school said in a tweet Friday night.
"There is an active shooter at the Van Vleet Oval. Take immediate action now. Run. Hide. Fight!" the University of Oklahoma said in a tweet just before 9:30 p.m. CT.
By 9:45 p.m. CT, another tweet indicated that campus police were investigating "possible shots fired" on the campus. "Avoid South Oval area. Shelter in place," the university said in the tweet.
This is a developing story and will be updated.