It abruptly ends years of efforts by prosecutors to see Patrick Crusius executed by lethal injection.
El Paso County District Attorney James Montoya said his decision in the prosecution of Crusius for one of the deadliest mass shootings in US history was driven by victims' families who wanted the case behind them.
"I could see a worst-case scenario where this would not go to trial until 2028 if we continued to seek the death penalty," he said on Tuesday.
Montoya acknowledged not all families agreed with the reversal by his office, which under previous leadership had committed to taking the case to trial and seeking the death penalty.
Under the plea offer, Montoya said Crusius would receive life in prison with no possibility of parole.
Crusius, 26, was already sentenced to 90 consecutive life sentences at the federal level after pleading guilty in 2023 to hate crime charges.
Under the Biden administration, federal prosecutors also took the death penalty off the table but did not explain why. In addition to the federal case, Crusius was also charged in state court with murder.
Montoya says he supports the death penalty and believes Crusius deserves it. But he said he met with the families of the victims and there was an overriding desire to conclude the process, though some relatives were willing to wait as long as it took for a death sentence.
"I'm just glad it's over," said Elise Hoffmann-Taus, whose father, Alexander Hoffmann was among those killed. "This is the outcome I wanted."
Crusius, who is white, was 21 and had dropped out of community college when he drove more than 1100 kilometres from his home near Dallas to El Paso.
Moments after posting a racist screed online that warned of a Hispanic "invasion" of the state, he opened fire with an AK-style rifle inside and outside the store.
Before the shooting, Crusius appears to have been consumed by the immigration debate, posting online in support of building the border wall and other messages praising the hardline border policies of President Donald Trump, who was in his first term at the time.
He went further in the rant he posted before the attack, saying Hispanics were going to take over the government and economy.
In the years since the shooting, Republicans have called migrants crossing the southern border an "invasion" and dismissed criticism that such rhetoric fuels anti-immigrant views and violence.
In the US government's case, Crusius received a life sentence for each of the 90 charges against him, half of which were classified as hate crimes.
One of his lawyers told the judge before the sentencing that his client had a "broken brain" and his thinking was "at odds with reality".
Federal prosecutors did not formally explain their decision not to seek the death penalty, but they did acknowledge Crusius suffered from schizoaffective disorder, which can be marked by hallucinations, delusions and mood swings.
The people who were killed ranged in age from a 15-year-old high school athlete to several grandparents.
They included immigrants, a retired city bus driver, teachers, tradesmen and several Mexican nationals who had crossed the US border on routine shopping trips.
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