Two people have died of injuries sustained in the El Paso, Texas, mass shooting, raising the death toll from the massacre there to 22.

In all, 31 were killed in back-to-back shootings in El Paso and Dayton, Ohio, shaking the nation and renewing the debate over gun violence.

The Del Sol Medical Center in El Paso said one died Sunday night, and the other Monday morning.

The medical center said it has five patients in stable condition and one patient in critical condition.

A 21-year-old Dallas resident suspected of the El Paso killings is in police custody.

The suspect, Patrick Crusius, is believed to have written a screed claiming responsibility for the attack and railing against what he called a "Hispanic invasion of Texas," investigators said.

Federal prosecutors have classified the case as domestic terrorism.

Claudia Duran, an administrator in the El Paso County district attorney's office, told NBC News that prosecutors intend to seek the death penalty.

The Dayton shooting took place in a popular entertainment district in the city's downtown area early Sunday. The shooter — who wore a mask, hearing protection and a bullet proof vest — was killed by police within about 30 seconds.

Authorities identified him as 24-year-old Connor Betts, and said a motive is under investgation.