An Army veteran of two Afghanistan tours who killed one person and wounded several others during a weekend rampage fired 212 rounds from his military-style rifle before a SWAT officer fatally shot him, police said Tuesday.

"Suffice to say, after he fired 212 rounds, he was prepared," police Lt. John McGalin said of ammunition carried by 25-year-old Dionisio Garza III, of Rancho Cucamonga, California.

McGalin said Garza was armed with an AR-15 rifle and a pistol and likely was experiencing a "mental health crisis" when he opened fire Sunday morning at a Houston auto detail shop, using the pistol to kill a customer, then retrieving the rifle and spraying the west Houston neighborhood, motorists and then police with gunshots.

"He was suffering from some depression, I guess you could say," McGalin said. "His family indicated he wasn't feeling right. And he left to come here to hang out with some friends and to try to find some work."

Garza's relatives have said he was haunted by his Afghanistan deployment.

Six people were wounded, including two officers and three motorists. McGalin said the sixth person wounded, John Wilson, 30, who initially on Sunday was considered a possible suspect in the outburst, was a nearby resident who armed himself after hearing all the gunfire and intended to try to assist in stopping Garza.

"He got outgunned, realized he was in a bad situation, tried to leave and was shot in the leg by the suspect when he tried to get to safety," McGalin said. "He was coming out to help. He didn't think very wisely, made a bad choice and got himself into a bad situation."

Wilson and the three other wounded civilians were hospitalized in stable condition. The two officers were released earlier.

Patrol vehicles were left bullet riddled and a police helicopter was hit with at least five shots.

McGalin said investigators believed Garza selected both the location and his victims at random. Detectives said he broke into an adjacent tire store late Saturday afternoon, then emerged Sunday morning with a pistol and shot 56-year-old Eugene Linscomb, a customer who had arrived moments earlier at the auto detail shop.

"Why he selected that location, there seems to be no rhyme or reason to it," he said. But McGalin said it appears Garza felt safe at that spot "due to his military training."

"He had access to three corners. He was backed up against a fence so he didn't have to worry about anybody coming from behind him. It was just a location he felt safe doing this. And that's the only thing we can surmise at this point in time until something different comes along," McGalin said.

He said detectives found some "random writings" at the tire store where Garza spent Saturday night but declined to elaborate.

"It doesn't appear to be a terrorism link to this or anything like that," he said. "It just appears to be someone who was in a mental health crisis."

Acting Police Chief Martha Montalvo said the investigation "is still evolving," with numerous witnesses yet to interview and evidence to examine.

She credited residents who called Sunday and then "opened up their homes to allow us to do what we had to do."

Police declined to be specific, but it appeared the SWAT officer who killed Garza nearly an hour after theshooting began was stationed more than 100 yards away at one of those homes.

"In my mind, they're heroes and averted what I believe could have been more casualties," Montalvo said.

Garza spent four years in the Army, receiving his discharge in 2014, according to Pentagon records released Tuesday. During that time, he served two tours in Afghanistan, the first from December 2009 to November 2010 and the second from December 2012 to August 2013. Assigned to infantry, he reached the rank of sergeant in December 2011.

"I think he was haunted by everything that he saw there and he experienced there," his stepmother, Cathy Garza, told ABC News. "I think it changes you. I don't know how you can go through what he went through and see what he saw and not have it change you or have it affect you."

Garza's family told Houston television station KPRC that something snapped in him following the two tours in Afghanistan and that his condition worsened in recent weeks.

"Just in the last two weeks it progressively got worse," said his father, Dionisio Garza. "It was not the same boy that we raised. Not the loving uncle, the loving brother.

"Something snapped. It wasn't him anymore. I'm not making excuses. No excuses. I know he did this, but it wasn't him anymore. My son was broken."