President Donald Trump has approved the U.S. military's execution of former Army psychiatrist Nidal Malik Hasan by firing squad, more than 17 years after he killed 13 people and wounded dozens more at Fort Hood, Texas.

The Pentagon announced Monday that War Secretary Pete Hegseth recommended the firing-squad execution and that Trump approved it. Pentagon spokesman Sean Parnell said the Secretary of the Army will determine the time and location of the execution.

Hasan was sentenced to death by a military jury in 2013 for the Nov. 5, 2009, shooting at the Texas military installation. The attack occurred at a medical facility at Fort Hood, where troops were preparing for deployments to Iraq and Afghanistan.

Thirteen people were killed, and 32 others were wounded in the attack. Hasan was shot and partially paralyzed by a civilian police officer who responded to the scene.

During his court-martial, Hasan represented himself and did not call witnesses or testify. Prosecutors presented evidence that he opposed the U.S. military operations in Iraq and Afghanistan and had communicated online with Anwar al-Awlaki, an American-born radical cleric associated with al-Qaida who was later killed in a U.S. drone strike in Yemen.

The execution would be the first carried out by the U.S. military since 1961. The case therefore marks the military's return to an execution method that has not been used by the armed forces in more than six decades.

Mass shootings at U.S. military installations remain relatively uncommon, although several deadly attacks have occurred in recent decades, including shootings at military facilities in Washington, Tennessee, Hawaii, and Florida.

Hasan's execution date has not yet been announced. The Secretary of the Army is expected to set the time and place for the execution.