A busy Walmart became a grisly crime scene Saturday morning when El Paso police say 21-year-old Patrick Crusius took aim at shoppers and store employees.

Another person died Monday morning, officials said, bringing the number of fatalities to 21. More than two dozen additional people were injured.

Here are five things to know about Crusius:

1.) From Allen, Texas. The suspect's last known address is in Allen, just north of Dallas. That's 650 miles away from where the shooting took place. Up until a few weeks ago, CBS News reports Crusius, 21, lived with his grandparents while attending nearby Collin College. "We are devastated by the events of El Paso and pray for the victims of this tragedy," the family said, in part, in a written statement Sunday.

2.) Used an AK-47. Intelligencer says video from the Walmart shows Crusius with an AK-47-style assault rifle and a large amount of ammunition. The shooting started in the parking lot before continuing inside the store.

3.) Manifesto posted. Minutes before the shooting, a racially charged manifesto believed to have been written by Crusius was posted on 8chan, an online forum. "This attack is a response to the Hispanic invasion of Texas," the manifesto said, in part, according to The New York Times. NBC News reported that Cloudflare, an internet hosting company, said Monday it was dropping 8chan as a client following the deadly shooting.

4.) Death penalty will be sought. El Paso County District Attorney Jaime Esparza said he intends to seek the death penalty, according to the New York Post. "The state charge is capital murder, and so he is eligible for the death penalty," Esparza said at a news conference. "We will seek the death penalty. The loss of life is so great, we certainly have never seen this in our community." In Texas, the death penalty is administered via lethal injection.

5.) Domestic terrorism. Almost immediately after the Walmart shooting, investigators labeled it as an act of domestic terrorism. John Bash, U.S. attorney for the Western District of Texas, said the crime was "designed to intimidate a civilian population." "We’re going to do what we do to terrorists in this country, which is deliver swift and certain justice," Bash said. The FBI's hate-crimes team has been activated to look into Crusius' past, the Texas Tribune says.