HUNTSVILLE, Ala. (AP) - Two 911 calls and a tweet about the possibility of an active shooter at a military installation set off a day of panic and confusion in Alabama.
The 911 calls came from within the Redstone Arsenal base near Huntsville and led the installation to tweet a warning to its 30,000 government employees, civilians and contractors: "run hide fight," the message said.
Police cars with flashing lights rushed to the scene and blocked entrances to the post, home to Army missile defense programs, NASA's rocket propulsion operations and federal law enforcement agencies. Even before any gunfire was confirmed, the governor offered her prayers and social media lit up with worried friends and families talking about the lockdown.
At one point, Redstone spokesman Christopher Colster acknowledged he didn't know whether the lockdown was part of a drill or an actual threat.
In the end, an investigation found that there was no active shooter and no shots were fired, said Col. Tom Holliday, the garrison commander. He said authorities would continue to investigate what happened, including whether the 911 calls were part of a hoax.
"We did have initial reports of someone hearing shots fired and someone seeing a weapon. That in itself drove us to our response," he said. "I would say that the situation that we live in in the United States today leads to caution. Honestly, if we have to overreact, I would rather overreact than underreact."
He said the phrase used in the tweet -- "run hide fight" -- is a standard response during an active shooter. An active shooter drill planned for Wednesday was canceled.
"We believe we have learned everything we needed to as part of the event today," he said, adding that the response worked as designed.
Images on social media showed an ambulance and what appeared to be civilians standing outside the Sparkman Center, which includes offices, an auditorium, cafeteria and an interior courtyard. Holliday said the 911 calls came from the Sparkman complex and that some people who evacuated the building needed medical attention unrelated to the 911 calls.
It took two hours to give the all-clear for the installation and another two hours to make sure that the sprawling Sparkman complex was secure.
Amy Jay said her husband, who was working at the Sparkman Center, was told the situation was over through an announcement over the building's public address system.
"Feeling like I can breathe again!" Jay wrote in a message to The Associated Press. "My husband is a contractor and a veteran so when we hear things like this we're reminded of what happened at Fort Hood," she said, referring to the 2009 shooting at a military base in Texas.
Alabama Gov. Kay Ivey's office said after the lockdown was lifted that she didn't know what led to the alert.