During Thursday night's Democratic debate in Houston, O'Rourke stated that he would push for a ban on the possession of AR-15s, the military-style assault rifle that is the weapon of choice for mass shootings, including the one in O'Rourke's hometown of El Paso, Texas, which left 22 people dead.
That is a far cry from his September 12, 2019, declaration, "Hell yes, we're going to take your AR-15".
O'Rourke's birth name is Robert Francis O'Rourke, and he has been mocked by Republican lawmakers for using his nickname, Beto.
Since O'Rourke's run for Senate, there have been several mass shootings across the USA, including in his hometown of El Paso, Texas, which he has said has changed his views on gun control.
He responded with his own tweet, saying, "This is a death threat, Representative. Clearly, you shouldn't own an AR-15-and neither should anyone else", O'Rourke tweeted in response, along with an image of Cain's tweet. Cain also called O'Rourke "a child".
The Republican talking point machine immediately began the messaging that all Democrats want to take all guns. The Washington Post reports that O'Rourke's staffers notified the Federal Bureau of Investigation about the tweet.
Cain did not respond to multiple requests for comment about his message. But his forceful "hell, yes" on Thursday became one of the most memorable lines of the presidential debate. Following the violence, O'Rourke stepped away from the campaign trail for almost two weeks to spend time supporting the community.
"I frankly think that that clip will be played for years at Second Amendment rallies with organizations that try to scare people by saying Democrats are coming for your guns". O'Rourke unveiled a proposal weeks after that shooting calling for a national gun registry, a nationwide gun licensing system and the mandatory buyback of assault-style rifles as part of his plan to curb gun violence and the rise of white nationalism. "People were murdered. The language you are using and the way you are using it is unsafe". The tweet was also reportedly sent to the Federal Bureau of Investigation as it threatens a presidential candidate.
Cain was elected to represent Texas House District 128 in 2016.
Congress is expected to weigh new controls in the wake of a series of mass shootings in the last two months, two of them in Texas, that stunned the nation.