Beto O’Rourke has already backed mandatory buybacks for assault weapons, but at Thursday’s Democratic debate, he left no ambiguity about what that would mean. “Hell, yes, we’re going to take your AR-15, your AK-47,” he said.

Less than an hour later, O’Rourke received what he described as a “death threat” from a fellow Texas politician. “My AR is ready for you Robert Francis,” Briscoe Cain, a Republican

Beto O’Rourke during the Sept. 12 Democratic presidential primary debate in Houston. Associated Press

state representative from the Houston area, wrote on Twitter, using O’Rourke’ legal name.

Cain did not respond to multiple requests for comment about his message. But many read it as clear threat of violence, and a spokeswoman for O’Rourke’s campaign told The Washington Post that staffers had reported the tweet to the FBI.

“This is a death threat, Representative,” O’Rourke wrote on Twitter. “Clearly, you shouldn’t own an AR-15 – and neither should anyone else.”

Cain shot back: “You’re a child Robert Francis.”

Twitter also took quick action, removing the lawmaker’s tweet roughly two hours after it appeared. A spokesman told The Post that it violated the company’s terms of service, which prohibit violent threats.

Thousands responded to the tweet before it was taken down, and Cain engaged with some. Asked if he had just threatened to shoot a presidential candidate and former member of Congress, he replied, “You’re an idiot.” When another critic told him they had saved a screenshot of his comments for the FBI, the lawmaker responded, “Cool bro.”

Cain’s provocation came shortly after a moderator at Thursday night’s debate asked O’Rourke if his proposal to require assault rifle owners to sell their weapons to the government amounted to taking away people’s guns. As The Post’s Amy B Wang reported, the former Texas congressman didn’t flinch, saying that assault weapons such as AR-15s and AK-47s were developed for combat, and use the kind of high-impact, high-velocity round that “shreds everything inside your body because it was designed to do that, so that you would bleed to death on a battlefield, not be able to get up and kill one of our soldiers.”

“When we see that being used against children,” he said, “hell, yes, we’re going to take your AR-15, your AK-47.”

Since Aug. 3, when a gunman armed with an AK-style rifle killed 22 people at a Walmart in O’Rourke’s hometown of El Paso, the candidate has been an outspoken proponent of stricter gun-control measures, including mandatory buybacks. He had previously supported banning the sale of new AR-15 rifles but stopped short of advocating for taking existing guns out of circulation, telling talk radio station KFYO in 2018, “If you purchased that AR-15, if you own it, keep it, continue to use it responsibly.”

Since the mass shooting in El Paso, O’Rourke has been emphatic about what a mandatory buyback would mean. Asked by a reporter earlier this month if he could address fears that the government was going to take away people’s assault rifles, he replied, “That’s exactly what we’re going to do.” But his forceful “hell, yes” on Thursday became one of the most memorable lines of the presidential debate. By the end of the night, it had turned into a slogan, appearing in red, white and blue letters on T-shirts sold on O’Rourke’s campaign website.

The proposal has widespread support among Democrats nationally – 74 percent support a mandatory buyback program, compared to 31 percent of Republicans, a recent Washington Post-ABC News poll found.

Cain’s assertion that his AR-15 was “ready” struck many as insensitive in light of the mass shootings that took place last month in El Paso and Odessa, Texas, where a gunman armed with an assault-style rifle killed seven and injured 22.

“In case you forgot, people were just killed in El Paso,” responded Mary E. Gonzales, a Democratic member of the Texas House. “People were murdered. The language you are using and the way you are using it is dangerous.”

Speaking to reporters after the debate, O’Rourke said that Cain’s comment “sure reads” like a death threat. “I think it’s a really irresponsible thing for him to do,” he added, “especially somebody who is a public servant and in a position of public trust to be sending that kind of message.”

Cain, an attorney, frequently uses his official social media accounts to air inflammatory and hyperbolic views. On Wednesday, for instance, he suggested on Twitter that the Texas legislature should “abolish” the famously liberal city of Austin.

First elected to the Texas legislature in 2016, Cain was ranked the most conservative lawmaker in the state’s House of Representatives the following year, and he also received the dubious distinction of appearing on Texas Monthly’s list of the 10 worst legislators in the state in 2017. Typically, the publication explained, freshmen lawmakers are exempted from the list, but they cited Cain’s “uninformed and belligerent performance.”

An outspoken supporter of Second Amendment rights, Cain was kicked out of the Texas Democratic Party convention in 2018 after he showed up with what appeared to be a sidearm and began handing out fake yard signs that said, “This home is a gun-free safe space,” the Fort Worth Star-Telegram reported.

The paper noted that when students across the nation left class to protest gun violence in the wake of a mass shooting that killed 17 in Parkland, Florida, last year, Cain responded by introducing legislation that would temporarily revoke state funding from any Texas schools where similar walkouts took place.

David Hogg, a former Parkland student and co-founder of March for Our Lives, argued that Cain’s tweet proved the necessity of mandatory buybacks.

“If you threaten to kill a presidential candidate you should not have a gun,” he wrote.