HOUSTON — A feud between Democratic presidential hopeful Beto O’Rourke and Houston-area Republican state Rep. Briscoe Cain could now have the FBI involved.

It all started during the Thursday night’s Democratic presidential debate held at Texas Southern University in as the candidates talked about mandatory gun buybacks in the wake of recent mass shootings.

“Hell yes, we are going to take your AR-15, your AK-47. We're not going to allow it to be used by fellow Americans anymore,” O’Rourke said.

Cain upped the ante when he posted a now-deleted tweet, “My AR-15 is ready for you, Robert Francis.” In response to O’Rourke’s declaration.

O’Rourke retweeted that calling it a “death threat.” And he doubled down at a post-debate party Thursday night, ”…who is a public servant."

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Cain of Deer Park said he didn’t even watch Thursday night’s Democratic presidential debate during which O'Rourke mentioned a mandatory assault weapon buyback.

Cain told KHOU 11 a friend messaged him about O’Rourke’s remarks and he felt the need to react.

“I mean, this is America, and we’re in Texas," Cain said. "And if the government was to come and maybe demand a couple of my guns, or all of them, I would still have more left because they’re never going to get them.”

O’Rourke has endorsed a mandatory federal buyback of assault weapons after a a gunman opened fire at a Walmart in his native El Paso, killing 22 people.

That allowed O'Rourke — who suspended his campaign for nearly two weeks to head home and attend vigils and visit victims who remained hospitalized after the mass shooting — to assert ownership of the issue of gun control in a way none of the other nine candidates onstage could.

O’Rourke reiterated during a post-debate interview that the tweet sure sounded like a threat to him.

"Well, I had no idea that it was going to go that way and that Robert Francis would get upset about it and take it as a threat," Cain said. "But I think the point was made.”

"I think it’s a really irresponsible thing for him to do," O'Rourke said. "Especially someone who is a public servant."

O’Rourke’s campaign confirmed it checked in with the FBI and Twitter removed Cain’s tweet. But KHOU 11 News legal analyst Gerald Treece said it probably doesn’t rise to a criminal level under what’s known as the “true threat doctrine.”

That’s because there was no clear and imminent ability for Cain to carry it out.

"I don’t see it going anywhere," Cain said. "It’s excited his base by trying to turn it into a threat and I think it’s helped, at least people that I know, understand that people want to take away their arms. They will not be taking our guns."

Cain said he’s heard from a lot of people on both sides and contacted DPS as a precaution to help keep his own family safe.

Meanwhile, the FBI could not confirm or deny any particular contact or the potential existence of an investigation.

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On a night that was supposed to feature sniping between White House hopefuls with better polling numbers, those rivals instead took time to praise O'Rourke.

"God love you for standing so courageously," Sen. Kamala Harris told O'Rourke.

Joe Biden said O'Rourke's post-shooting effort in El Paso was "meaningful," and the former vice president created a lighthearted moment when he offered: "Excuse me for saying Beto. Congressman O'Rourke."

O'Rourke responded: "That's all right. Beto's good," drawing laughter and applause from the audience at TSU.

Even Sen. Cory Booker saluted O'Rourke while noting that, in communities of color, ordinary gun violence claims more lives than mass shootings that grab national headlines do. "We must awaken a more courageous empathy in this country," Booker said.

In the wake of the El Paso shooting, O'Rourke has remade his presidential bid. He has focused more on the urgent need to curb gun violence. He has decried what he calls racism on President Donald Trump's part. He is still frequently traveling to the states that kick off presidential primary voting: Iowa, New Hampshire, Nevada and South Carolina. But he has also visited an Arkansas gun show and said there's more bipartisan agreement on the need for federal firearm limits than many believe.

To be sure, praise from his presidential rivals may indicate that they no longer see O'Rourke as a serious threat. Fresh off nearly upsetting Republican Sen. Ted Cruz in the nation's largest red state last November, O'Rourke burst into the race for the White House in March only to see his once promising polling and fundraising decline sharply.

O'Rourke's supporters had looked to the first two Democratic debates in Miami and Detroit for strong performances that could lift their candidate back among the crowded field's top tier — but found his efforts lacking. This time, O'Rourke didn't schedule public events in the days leading up to the Houston debate, freeing up time to prepare.

That led to O'Rourke appearing more confident and poised than during previous debates, and answers that seemed unfocused in the past were far crisper Thursday.

To start the debate, O'Rourke said the gunman who drove 600-plus miles to El Paso, on the Texas-Mexico border, after posting an anti-immigrant screed online was "inspired to kill by our president."

Tim Murtaugh, a spokesman for President Donald Trump's reelection campaign, responded on Twitter that O'Rourke is "as desperate as he can be." The shooter had insisted his opinions "predate Trump and his campaign for president."

But after his "Hell yes" moment, O'Rourke looked anything but desperate. A short time later, his campaign riffed off fellow presidential hopeful and Massachusetts Sen. Elizabeth Warren's having a "plan" for everything with a fundraising tweet featuring an image of a military-style rifle over the caption, "Beto has a ban for that."

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