(CNN) –Reports of a shooting early Monday outside a Walmart in Duncan, Oklahoma, prompted a brief lockdown of the city’s schools, officials said.

Details of the incident were slim, but in separate social media posts, the Duncan police said they were aware of the reports and Duncan Public Schools said it was locking down its schools and visitors would not be allowed to enter until police declared the situation safe.

Less than an hour later, the school system said it had ended the lockdown after getting the all clear from authorities.

CNN affiliates KOCO and KSWO, citing state police, reported fatalities.

An aerial view of the Walmart, which sits next to a strip mall, showed a large swath of the parking lot cordoned off in yellow crime scene tape. Several emergency vehicles were in the parking lot.

This is a developing story.