EL PASO, TX — Authorities are searching for answer about why a rifle-wielding gunman shot dozens of people at a packed Walmart store in El Paso, killing 22 people and wounding 26 more. Specifically, investigators were looking Sunday into whether the mass shooting was a hate crime after a manifesto posted online prior to the attack said the massacre was in response to the “Hispanic invasion of Texas.”

Gunfire erupted around 10:40 a.m. Saturday as back-to-school shoppers packed the store near the Cielo Vista mall to capacity, police said. Shortly thereafter, the suspect witnesses described as calm and methodical surrendered without incident. The death toll rose to 22 Monday after two more of the shooting victims died.

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A federal law enforcement official who spoke to Patch identified the shooter as Patrick Crusius, 21, of Allen, Texas. Multiple other media outlets reported the same.

NEW: El Paso shooting suspect mug shot just released, Patrick Crusius, 21. pic.twitter.com/o3VMTAAOt0
— Daniel Borunda (@BorundaDaniel) August 4, 2019

Here are five things to know about Crusius:

1. A hate-filled manifesto was published online just 19 minutes before the first 911 call, The New York Times reported. The manifesto included anti-immigrant sentiments and referenced the mass slaughter in New Zealand, with the words printed over top an image of a naked man holding a black handgun. The graphic photo includes male genitalia and the American Flag.

“In general, I support the Christchurch shooter and his manifesto,” the document reads. “This attack is a response to the Hispanic invasion of Texas.”

The author added: “I am simply defending my country from cultural and ethnic replacement brought on by an invasion.”

Investigators are operating under the assumption the manifesto was written by Crusius and are exploring hate crime, terrorism and civil rights charges.

2. The suspect told investigators he wanted to shoot as many Mexicans as possible, two law enforcement officials told ABC News.

3. The shooter used an AK-47-style rifle and carried several magazines to the Walmart, ABC News reported. Witness said he appeared calm and looked like he was “on a mission.”

One witness told Fox News the gunman was “just pointing at people and shooting straight at them.” She saw three or four people fall to the ground.

4. Crusius reportedly attended Liberty High School and then graduated from Plano High School before attending Collin College from fall 2017 through spring 2019, the college confirmed.

“We are saddened and horrified by the news of the shooting today in El Paso, Texas,” the college wrote in a Facebook post Saturday.

5. Crusius was “very much a loner, very standoffish,” former neighbor Leigh Ann Locascio told the Los Angeles Times. She said he always sat alone on the bus in junior high school and high school. He also expressed negative views of kids in the school band on sports teams.

Tony Locascio, her son, routinely walked to school with Crusius and his sister and said Crusius used to walk ahead of or behind them. He didn’t talk to them and always kept to himself.

“He wouldn’t talk to people,” Tony Locascio said. “No one really knew him.”