Investigators searched Lopez's home on Thursday and questioned his wife, who declined to comment in Spanish when reached by phone by The Associated Press.
Lopez walked into a base building around 4 p.m. Wednesday and began firing a .45-caliber semi-automatic pistol. He then got into a vehicle and continued shooting before entering another building on the Army post. He eventually was confronted by military police in a parking lot, Milley said.
As he came within 20 feet of a police officer, the gunman put his hands up but then reached under his jacket and pulled out his gun. The officer drew her own weapon, and the suspect put his gun to his head and pulled the trigger a final time, Milley said.
The base's commander praised the actions of the female police officer but declined to release her name. Milley also said authorities were first alerted to the rampage when two soldiers who had been shot managed to dial 911, and that a base chaplain shielded soldiers with his own body before smashing window glass to allow them to flee the area.
Lopez bought the weapon he used in the attack at Guns Galore in Killeen — the same store, just off the base, where Army psychiatrist Nidal Hasan purchased an FN 5-7 tactical pistol that he used it to kill 13 people and wound more than 30 others in a November 2009 shooting on the base.
After that shooting, which marked the deadliest attack on a domestic military installation in U.S. history, the military tightened base security nationwide.
Lopez grew up in Guayanilla, a town of fewer than 10,000 people on the southwestern coast of Puerto Rico, with a mother who was a nurse at a public clinic and a father who did maintenance for an electric utility company.
Glidden Lopez Torres, who said he was a friend speaking for the family, said Lopez's mother died of a heart attack in November.