Updated 1:44 PM EST
According to the Davis-Monthan Air Force base Twitter account, the lockdown has been lifted and "base personal were free to resume all normal operations."
TUCSON, Ariz. — Davis-Monthan Air Force base in Arizona was on lockdown Monday after unconfirmed reports of gunshot sounds.
Officials posted on the base Facebook page that people should seek shelter.
A charter school for grades 6 to 12 said on its Twitter account that it's not allowing anyone to enter or leave the school.
Tucson police said they had not been asked to assist.
No further information was available.
The Tucson base is home to the 355th Fighter Wing, which provides training and deploys the A-10 jet.
About 6,500 active duty military and 1,000 Reserve and Air National Guard personnel work on the base, along with about 3,000 civilians.