"I believe we saw very clearly that the actions of our first-responders was spot-on", Holliday said.
There are no reports of injuries yet, but CNN reported that an ambulance service and Federal Bureau of Investigation agents had been sent to the facility. Redstone spokesperson Christopher Colster said that the lock down was not a drill, and that there weren't any injuries immediately reported.
Nearby hospitals said they have not received official word from the base concerning an active shooter, but are prepared in the event they are needed.
Gates to the complex were initially closed, however some were reopened, and movement on streets nearby was restricted.
The Arsenal's Twitter account posted that the "installation is locked down".
A lockdown still is in effect for one Redstone Arsenal building where a possible shooter had been reported Tuesday morning, but an all-clear has been announced for everywhere else at the northern Alabama army post, facility spokeswoman Kim Hanson said.
One Hong Kong, two sentiments after 20 years of Chinese rule
Lam, 59, won the election of the fifth-term chief executive of the SAR in March, vowing to lead Hong Kong forward in solidarity. The stock of China Unicom ( Hong Kong ) Limited (ADR) (NYSE: CHU ) has "Buy" rating given on Thursday, February 4 by HSBC.
Two 911 calls came from the base shortly before 10 a.m., and the installation soon tweeted a warning that included the message, "Run hide fight".
Holliday said this is an isolated incident and that the initial callers claimed they heard shots and saw a possible gunman.
But Colster would not say whether the active shooter report was part of that exercise, adding: "I really can't say at this point what happened". Installation is locked down.
Before the lockdown was lifted, Alabama Gov. Kay Ivey's office said it couldn't provide any details.
An Alabama military post says in tweet it is on lockdown amid reports of possible active shooter. The vast majority of people on the arsenal are civilians with less than 1,500 uniformed personnel.
Redstone also is home to Army Materiel Command, Marshall Space Flight Center, Bureau of Alcohol, Tobacco, Firearms and Explosives and FBI facilities.
Redstone Arsenal is located in Madison County, Ala., which is south of Huntsville near the Huntsville International Airport.