Texas' Joint Base San Antonio-Lackland is on "active shooter lockdown," according to the base's Facebook page.
"All base personnel implement LOCKDOWN procedures and immediately take cover," the base posted on Facebook and Twitter.
Joint Base San Antonio comprises three locations, including Lackland, located in western San Antonio. The base is the largest joint base of the Department of Defense, according to the base website.
This is a developing story and will be updated.