(CNN) -- There is an active shooter at the sprawling central Texas base of Fort Hood, a source at Fort Hood told CNN on Wednesday. The situation is serious and sirens are going off, said the source, who spoke on the condition of anonymity. A spokesman for the base said an "incident" was under way but declined for provide additional information. Fort Hood's official Twitter feed asked that all personnel on post shelter in place. A local sheriff's office said that it had heard there was a shooting. "They got some kind of shooting incident going on. They haven't told us anything. It was on post and being handled by the military. Fort Hood has not asked for any assistance," said Lt. Donnie Adams with the Bell County Sheriff's Office. On November 5, 2009, Army Maj. Nidal Malik Hasan opened fire at Fort Hood, killing 13 people and injuring 32. The former Army psychiatrist was convicted of premeditated murder, and a military jury recommended that Hasan be put to death.