A frightening day at Davis-Monthan Air Force Base ended peacefully Friday after a daylong lockdown spurred by fears that a gunman might be on the loose inside the military installation.

D-M purposely kept the media and public in the dark for several hours during the incident, adopting an information blackout after SWAT teams, hostage negotiators and the FBI descended on the base and police closed the area to vehicle traffic.

In the absence of concrete information, social-media sites such as Facebook and Twitter exploded with rumors and false reports of gunfire and numerous casualties, striking fear in the hearts of some D-M personnel serving overseas.

"Please, I'm deployed. Can anyone tell me if my wife and baby are safe?" one airman pleaded in a Facebook posting.

Nationwide, many news outlets, including the Arizona Daily Star, also reported erroneously that a man was barricaded on base in a standoff situation.

After seven anxious hours, a D-M official finally announced there was no gunman.

The incident began about 11 a.m., when base security received a report that someone carrying what looked like a weapon may have entered a building on base that is near dormitories and a dining facility.

That sent the installation into lockdown, with entrances blocked to all but emergency vehicles.

As the day unfolded, hundreds of Tucson parents whose children go to school on base were told their kids were safe but they were not allowed to pick them up until further notice.

About 12:30 p.m. a D-M news release said the matter was still being investigated but that "no shots have been fired and no one has been hurt."

An hour or so later, a call went out on Tucson's emergency-response radio system summoning Tucson Police Department's SWAT teams and hostage negotiators to the air base.

TPD also announced then that it was shutting down East Golf Links Road bordering the base, and the FBI confirmed agents from Tucson and Phoenix were on the scene.

Three hours went by with no further word from D-M about what was occurring.

At 4 p.m. the base reopened its gates to parents picking children up from schools or day-care centers.

At 5 p.m. a D-M news release said the situation was over, and that information about it was purposely withheld so "the suspect" wouldn't be tipped off about steps being taken to track him down.

It wasn't until 6 p.m. that D-M's wing commander, Col. John Cherrey, told reporters gathered outside the base that there was no gunman.

After a thorough search of the building in question, "no gunman or weapon was found," Cherrey said.

"All reports and threats regarding the safety and security of our airmen and their families are taken very seriously," the colonel said

Around midday, several firetrucks and ambulances entered the base with lights and sirens on. One of them picked up a woman on base who had gone into labor during the lockdown.

Contact reporter Carol Ann Alaimo at calaimo@azstarnet.com or at 573-4138.