Beto O'Rourke once again called President Donald Trump a "white supremacist" during the Democratic Party's 2020 debate on Thursday night, saying that the USA leader "poses a mortal threat to people of color".
It read, "My AR is ready for you Robert Francis".
O'Rourke's campaign is now selling t-shirts with the caption, "Hell yes, we're going to take your AR-15". "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.
"You know, I called this out in no uncertain terms on August 3rd - and every day since then - and I was talking about it long before then, as well", O'Rourke replied.
Cain did not respond to multiple requests for comment about his message.
Thousands responded to the tweet before it was taken down, and Cain engaged with some.
"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, in Midland, there weren't enough ambulances to get to them in time".
Sen. Cory Booker of New Jersey needled O'Rourke later, saying he was sorry it had taken the El Paso shooting for O'Rourke to embrace the position Booker already held, backing a mandatory buyback and national registration. 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". But his forceful "hell, yes" on Thursday became one of the most memorable lines of the presidential debate.
A spokesman for Mr O'Rourke said the Texas state legislator had been reported to the Federal Bureau of Investigation.
Earlier this month, he wrote on Twitter, addressing O'Rourke, "I'll give you my gun when you pry it from my cold dead hands".