After 17 people were killed in a Parkland, Florida, school shooting, Republican donor Al Hoffman Jr. announced that he will not donate to electioneering groups or candidates unless they support an assault weapons ban. Hoffman’s ultimatum goes against the conventional GOP stance of considering any new gun control measures anathema.

Alexander Burns of the New York Times reported that the Florida-based donor, a retired real estate developer and former ambassador to Portugal, sent Republican leaders like Jeb Bush and Florida Gov. Rick Scott an email that read, in part, “I will not write another check unless they all support a ban on assault weapons. Enough is enough!” Hoffman also made clear that he wouldn’t back Scott, who may run for Senate this year and who said, in the wake of the 2016 Pulse nightclub shooting, “The Second Amendment didn’t kill anybody.”

Hoffman has given millions to Republican causes and candidates, including $25,000 to the Mitch McConnell–aligned Senate Leadership Fund in 2017 and more than $1 million to the super PAC Right to Rise, which backed Jeb Bush’s presidential campaign. Hoffman also told the Times that he planned to reach out to “every single donor I know in the Republican party” and ask each one to join his boycott.

Hoffman’s frustration may stem from the Republican response to the Parkland shooting, which has been more of the same: Paul Ryan cautioned against “knee-jerk” reactions. Trump said the country needed to “tackle the difficult issue of mental health.” Rick Scott, pressed by CNN’s Wolf Blitzer on whether he was “ready to commit [his] political team to tighten gun control, gun restrictions in the state of Florida,” said, “Everything’s on the table,” a non-answer that is still the closest he’s gotten to supporting gun control. Given this response and the National Rifle Association’s stranglehold on the GOP, even Hoffman admitted it was “not likely” his boycott would affect the party’s position on gun regulations.

In early 2016, Hoffman’s contributions to the presidential race ranked him 58th among major donors, according to the New York Times; Robert Mercer had donated 11 times as much money. But while Hoffman may not have quite the political heft of a Koch or Mercer, it’s refreshing to see a Republican donor speak out against assault weapons and then put his money where his mouth is.