Immediately prior to the shooting, Lopez went to the 49th Transportation Battalion administrative office where he tried to obtain a ten-day leave form so he could attend to "family matters".

At approximately 4:00 p.m., he returned and opened fire with a .45-caliber Smith & Wesson M&P pistol inside the same building, injuring three soldiers‍— PFC Wilfred Sanchez, Sgt.

First Class Daniel Ferguson, who was attempting to barricade a lockless conference room door to prevent Lopez from gaining entry and harming anyone inside.

[6] Lopez then got into his car and drove slowly to a motor pool building to which he had been assigned, firing at two soldiers and wounding one of them along the way on 73rd Street.

Reaching the medical building, Lopez shot and wounded 1st Lt. John Arroyo Jr., in the throat as he was walking outside in the western parking lot.

Then, Lopez walked down the main hallway, wounded MAJ Patrick W. Miller, shooting him point blank in the abdomen, and exited through a doorway.

They were identified as:[17][18] During the shooting, the Bell County Communications Center dispatched deputies and troopers from the Texas Department of Public Safety to the nearby post after receiving reports of an "active shooter", sheriff's Lt. Donnie Adams said.

[24] On January 23, 2015, the Army concluded from an investigation into the shooting that there was no indication of a possibility of violent behavior from Lopez through his medical and personnel records.

Previously, in the wake of the aforementioned 2009 Fort Hood shooting, information sharing regarding medical history was among 78 recommendations suggested to identify the risk of violent behavior.

He enlisted in the Puerto Rico National Guard on January 4, 1999, but was unable to pass a required English language course and was subsequently discharged on November 30 of the same year.

[6] Lopez was allegedly distraught over financial issues and the deaths of his grandfather and then his mother during a two-month period five months prior to the shooting.

[29] During a press conference on the day of the shooting, Fort Hood Commander Mark A. Milley stated that Lopez died of a self-inflicted gunshot wound.

[6][17][26][27] He had previously purchased a firearm of the same model, unregistered with the installation, on February 23, although he reported it stolen on March 1, the same day he bought a replacement.

[15] In his Facebook account, Lopez made posts in which he alleged that he was robbed by two men in early march and also criticized Adam Lanza, the perpetrator of the Sandy Hook Elementary School shooting in 2012.

[26] On March 24, Lopez's battalion began tracking a ten-day permissive temporary duty (PTDY) request he made immediately after arriving to Fort Hood so he could help his family relocate to an apartment in Killeen, as his current one was burglarized.

Though the corrected form was signed, it did not have a control number, which is reported to have led to the conflict in the 49th Transportation Battalion office that sparked the shooting.