The Army approved on Friday the Purple Heart for soldiers killed and wounded in a 2009 attack on Fort Hood, Texas. (Photo by Sgt. Michael Selvage/ Army)

Army Secretary John McHugh said Friday that he has approved awarding the Purple Heart and its civilian counterpart to those wounded during a mass shooting at Fort Hood, Texas, in 2009, following years of pressure from families and a change in rules approved by Congress.

The Nov. 5, 2009, shooting killed 13 people and wounded more than 30. It was carried out by Maj. Nidal Hasan, an Army psychiatrist, who was convicted in August 2013 of 13 counts of murder and 32 counts of attempted murder. Hasan said he acted because of what he alleged was U.S. aggression against Muslims and the wars in Iraq and Afghanistan. He offered no apology during trial, and was sentenced to death.

The lack of recognition for those killed and wounded in the attack had angered some victims and their families and prevented them from receiving combat-related benefits. The medal is typically awarded for wounds in a war zone, but the Army’s criteria for the award says it also can be authorized in other situations, including international terrorist attacks against the United States.

[READ: The fight to get Fort Hood shooting victims Purple Hearts clears a hurdle]

The Army declined to call Hasan’s attack international terrorism, however. That led Congress to include a provision in the 2015 National Defense Authorization Act that required the Defense Department to review the Fort Hood case for Purple Heart recipients.

McHugh said in a statement that the criteria for the Purple Heart and its civilian counterpart, the Defense of Freedom Medal, had prevented the Army from approving the medals. Congress has expanded eligibility by redefining an attack by a “foreign terrorist organization” to include an incident in which an individual involved was in communication with a foreign terrorist organization beforehand and the attack was inspired or motivated by it, he said.

“Now that Congress has changed the criteria, we believe there is sufficient reason to allow these men and women to be awarded and recognized with either the Purple Heart or, in the case of civilians, the Defense of Freedom medal,” McHugh said. “It’s an appropriate recognition of their service and sacrifice.”

Before the attack, Hasan had communicated numerous times with Anwar al-Awlaki, a radical American-born cleric who served as one of the chief propagandists for al-Qaeda in the Arabian Peninsula, which operates from Yemen. The cleric was killed in a U.S. drone strike in Yemen in 2011.

The Pentagon had previously treated the Fort Hood as a “workplace violence” incident. Last year, the Pentagon said that adhering to “the criterion for award of the Purple Heart is essential to preserve the integrity of the award.”

“To do otherwise,” it said in a position paper, “could irrevocably alter the fundamental character of this time-honored decoration.”