Gunman in Johnson Space Center: or is he??

From Yahoo/AP:

HOUSTON - A Johnson Space Center building was evacuated Friday after reports of a gunman inside, Houston police said. Police were called about 1:40 p.m. for Building 44, which houses communications and tracking development laboratory, news reports said.

Johnson Space Center security officers and Houston police, including a SWAT team, were dispatched to the scene.

NASA spokesman Bill Jeffs said he could not confirm whether there was a gunman or whether any shots were fired.

"It's an ongoing situation," he said.

If there is no gunman, what situation??