File handout photo of the main gate at the U.S. Army post at Fort Hood

Fort Hood was placed on lockdown Wednesday after four people were killed in a shooting on the Texas military base, officials said.

The gunman, identified as 34-year-old soldier Ivan Lopez, died of a self-inflicted wound, the Justice Department said.

According to KCEN-TV, at least 14 people were injured in the shooting. The wounded were transported to Carl R. Darnall Medical Center and other local hospitals, Fort Hood officials said.

A spokesman for Fort Hood confirmed to Yahoo News that a shooting took place, but additional details were not immediately available.

Emergency crews, FBI and SWAT teams were called in to the base following the shooting, which occured at approximately 4:30 p.m. local time at a medical support building on the sprawling base. Soldiers and area residents were ordered to shelter in place, as police pursued a possible second “active” shooter.

President Barack Obama said the White House was monitoring reports of the shooting.

“We’re following it closely. The situation is fluid right now,” Obama told reporters, adding that investigators will “get to the bottom of exactly what happened.”

“We’re heartbroken something like this might have happened again,” the president said.

In 2009, 13 people were killed and more than 30 wounded in a mass shooting at the base carried out by then-Maj. Nidal Hasan, an army psychiatrist. A U.S. Senate report following the incident described it as the worst attack on American soil since the terrorist attacks of Sept. 11, 2001 although the FBI said Hasan had no formal ties to terrorist groups despite having expressed anti-American viewpoints prior to the shooting.

Hassan was sentenced to death after admitting during his August 2013 court martial hearing to the mass shooting. He is now on death row.