ALLEN, Texas (AP) — The shooter with neo-Nazi leanings who killed eight people at a suburban Dallas shopping mall brought eight legally purchased guns to the scene, apparently chose his victims randomly and was shot dead by police within four minutes, authorities said Tuesday.

The Allen police officer who shot and killed 33-year-old Mauricio Garcia, ending Saturday's attack, acted heroically and saved "countless lives" through his quick action, Hank Sibley, the regional director of the Texas Department of Public Safety, said at a news conference. He said the officer is still processing what happened and isn't ready to have his name made public.

"If he hadn't have been there, I think we'd have had a much more severe situation," Sibley said.

The investigation into Garcia's motive is ongoing, but he expressed neo-Nazi beliefs, Sibley said, adding that Garcia had no criminal history before he opened fire at Allen Premium Outlets.

Garcia brought eight guns to the scene, including three that he had on him and five that were still in his vehicle, Sibley said. Garcia obtained all of the weapons legally.

"The big question that we're dealing with right now is, 'What's his motive? Why did he do this?'" Sibley said. "Well, the big question is, we don't know. That's what the investigation is trying to find out."

Posts by Garcia on a Russian social networking site suggest that he planned for weeks before he launched the attack in Allen, a diverse community of about 100,000 people roughly 25 miles (40 kilometers) north of downtown Dallas.

Garcia researched when the mall was busiest — Saturday afternoons — and posted photos on social media in mid-April of a store near where he ultimately began shooting people. Among those killed were two elementary school-age sisters, a couple and their 3-year-old son, and a security guard.

An Associated Press review of his online activity shows he displayed a fascination with white supremacy and mass shootings, which he described as sport. Photos Garcia posted showed large Nazi tattoos on his arm and torso, including a swastika and the SS lightning bolt logo of Hitler's paramilitary forces.

The online statements have contributed to an emerging picture of Garcia. He was discharged from the Army in 2008 because of mental health issues and apparently had been working as a security guard, according to neighbors and an Army official.

Aric Toler, director of training and research at the international research collective bellingcat.com, said he identified Garcia's profile on the site OK.RU by searching for active accounts with his birthdate located in the U.S. The AP independently verified the account, which also featured an image of a traffic ticket with Garcia's name and birthdate as well as paperwork from a motel where he stayed before the shooting at Allen Premium Outlets in one of the Dallas' most diverse suburbs.

Federal agents investigating what motivated the shooting have also reviewed the online posts, according to a federal law enforcement official who could not discuss details of the investigation publicly and spoke to the AP on the condition of anonymity.

The official also said Garcia had a patch on his chest when police killed him that read "RWDS," an acronym for the phrase "Right Wing Death Squad," which is popular among right-wing extremists and white supremacy groups.

Investigators have also interviewed family members and associates of Garcia to ask about his ideological beliefs and are examining his financial records and other electronic media, the official said.

Garcia joined the Army in 2008 but was terminated three months later without completing his initial training, U.S. Army spokeswoman Heather J. Hagan said.

According to an Army official who spoke on the condition of anonymity to discuss personnel issues, he was kicked out due to mental health issues.

Garcia received an "uncharacterized" discharge, which is common for recruits who don't make it through training or the first 180 days, according to a defense official who also spoke on condition of anonymity to discuss personnel issues. That type of discharge — which is not dishonorable — would not set off red flags or require any reports to law enforcement.

On the Dallas block where Garcia lived with his parents until recently, neighbors said they thought he worked as a security guard but they weren't sure where. The company that manages the mall where the attack happened didn't immediately reply to messages seeking further information.

Sibley said Tuesday that as far as he knew, Garcia hadn't worked at the Allen mall, but that he wasn't completely sure.

A woman who lives next door to Garcia's parents' house said she didn't know her neighbors well but described them as nice and polite. Garcia was always friendly, waving and honking, she said.

A law enforcement official said investigators also have searched a Dallas motel where Garcia had been staying in the runup to the attack.

The shooting was the latest attack to contribute to the unprecedented pace of mass killings this year in the U.S. Just over a week before, five people were fatally shot in Cleveland, Texas, after a neighbor asked a man to stop firing his weapon while a baby slept, authorities said.

The community mourned the dead and awaited word on the seven people who were wounded. Medical City Healthcare said Monday it was treating six patients: Three were in critical condition, two were in fair condition and one was in good condition at a children's hospital. Police said a seventh wounded person was taken to a different hospital.

Allen is one of the area's most diverse cities. The area saw the largest Asian American growth rate of any major U.S. metro area, according to U.S. Census figures. Those statistics show that Allen's population is about 19% Asian, 10% Black and 11% Hispanic.

Allen also is connected to another of Texas' recent mass shootings. Patrick Crusius lived there in 2019 before he posted a racist screed online warning of a "Hispanic invasion" and drove to El Paso, where he opened fire at a Walmart, killing 23 people. Crusius, 24, pleaded guilty to federal hate crime and weapons charges in February.

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Baldor reported from Washington and Johnson from Seattle. Jamie Stengle and Adam Kealoha Causey in Dallas; Michael Balsamo in Washington; Vanessa Alvarez in New York; James Vertuno in Austin; Michelle R. Smith in Providence, Rhode Island; and Rebecca Boone in Boise, Idaho, contributed to this report.