At the third Democratic debate Thursday night, former Texas Rep. Beto O’Rourke declared to the enthusiastically affirming crowd that “Hell yes” he is going to take Americans’ “weapons of war” from them. During the debate, O’Rourke’s account posted a gun control-themed tweet with a borrowed tagline and an image of a weapon that sparked immediate mockery from pro-Second Amendment advocates. After the debate, O’Rourke got into an online feud with a Republican Texas state lawmaker over a comment O’Rourke condemned as a “death threat.”

As highlighted over at Twitchy, during the debate O’Rourke’s account posted a tweet that presented a version of fellow Democratic presidential candidate Elizabeth Warren’s (D-MA) “Warren has a plan for that” slogan:

O’Rourke’s critics quickly pointed out that the gun the Democratic presidential hopeful featured in his fundraising tweet, which has a grenade launcher attachment, is already illegal.

Among those who had some fun with O’Rourke over the post include RealClearInvestigations’ Mark Hemingway and former NRA spokesperson Dana Loesch, who noted that grenades and grenade launchers have been illegal for decades under the National Firearms Act of 1968. The gun Beto chose to feature has some other problems as well, including its suppressor. If it’s fully automatic, that’s also fully illegal.

Another critic who responded to O’Rourke’s declaration Thursday night that he was going to take Americans’ guns from them was a fellow Texas lawmaker, State Rep. Briscoe Cain (R), who quoted O’Rourke’s instantly viral line announcing, “Hell yes we’re going to take your AR-15” — which the candidate had promptly tweeted out — by letting him know that his own AR-15 was “ready” for him.

“My AR is ready for you Robert Francis,” tweeted Cain responding to O’Rourke’s statement (h/t The Hill).

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

“You’re a child Robert Francis,” Cain responded.

During the debate Thursday, O’Rourke was asked if he is really serious about confiscating Americans’ legally owned “assault-style weapons.” O’Rourke answered emphatically that he is.

“Some on this stage have suggested a voluntary buyback for guns in this country,” ABC News host David Muir said in a question directed to O’Rourke. “You have gone further. You said, quote, ‘Americans who own AR-15s and AK-47s will have to sell them to the government, all of them.’ You know the critics call this confiscation. Are you proposing taking away their guns and how would this work?”

“I am, if it is a weapon that was designed to kill people on a battlefield,” said the candidate to heavy applause, which erupted before he even finished the line. “If the high impact high velocity round, when it hits your body, shreds everything inside of your body because it was designed to do that so that you would bleed to death on a battlefield and not be able to get up and kill one of our soldiers. When we see that being used against children and in Odessa. I met the mother of a 15-year-old girl who was shot by an AR-15. And that mother watched her bleed to death over the course of an hour because so many other people were shot by that AR-15 in Odessa and Midland [that] there weren’t enough ambulances to get to them in time.”

O’Rourke then made the declaration that would make headlines and that he would quickly tweet out: “Hell yes we are going to take your AR-15, your AK-47. We are not going to allow it to be used against fellow Americans anymore.”

Related: Beto Says ‘Hell Yes’ We’re Going To Take Americans’ Guns; WATCH How Democratic Crowd Responds