The man charged in the El Paso Walmart mass shooting is on suicide watch, authorities say.

Patrick Crusius, charged with killing 22 and injuring 25 on Aug. 3 was placed under close guard Monday on the recommendation of medical staff at the county jail, according to an El Paso County Sheriff's Office official.

Crusius, a 21-year-old white male from a Dallas-area neighborhood, has been in custody since Aug. 3 without bond shortly after the shooting, according to a police affidavit.

Crusius was separated from other inmates and placed a single jail cell at the Downtown jail, according to the sheriff's office. He has been in the jail under a capital murder charge since Aug. 4.

The U.S. Attorney's Office is also investigating the case with the possibility of filing federal hate crime and domestic terrorism charges against Crusius, according to John Bash, of the Western District of Texas.

Crusius was taken into custody without incident by law enforcement responding to the scene, El Paso Police Chief Greg Allen said at an Aug. 4 news conference.

"When he saw the officers approaching the scene where he was at, he basically surrendered," Allen said.

He allegedly confessed to the mass shooting to officers as he was surrendering, according to a police affidavit, and admitted to targeting Mexicans. He left his home in suburban Dallas to drive about 10 hours with the intent to kill Hispanics, authorities believe. Crusius, who is white, laced his manifesto with anti-immigrant and racist rhetoric, saying he advocated a plan to divide the nation into territories by race.

Those killed ranged in age from 90 years old to a 15-year-old high school student.

It’s believed Crusius used an AK-47-style gun to gun down people at the Walmart. He is believed to have posted an online manifesto referencing a weapon similar to the AK-variant semi-automatic rifle seen in surveillance video from the El Paso Walmart.

"It was not done by an El Pasoan. No El Pasoan would ever do this," El Paso Mayor Dee Margo said right after the shooting. "I don’t know how to deal with evil. I don’t have a textbook with dealing with evil other than the Bible. I’m sorry."

Allen said at the Aug. 4 news conference that the suspected shooter was forthcoming with information after his arrest.

"He basically didn’t hold anything back," Allen said.

El Paso County Magistrate Judge Penny Hamilton appointed San Antonio lawyer Mark Stevens to represent Crusius.

Aaron Montes may be reached at 915-546-6137; amontes@elpasotimes.com; @aaronmontes91 on Twitter.