Al Hoffman Jr., a Florida-based real estate developer who previously served as the National Finance Chairman for the Republican National Committee (RNC), told GOP leaders in an email Saturday that he will no longer support them until they take action on gun violence, the New York Times reported.

"I will not write another check unless they all support a ban on assault weapons," Hoffman wrote, according to the Times. "Enough is enough!"

Hoffman has donated millions of dollars to GOP causes and politicians, including Florida Gov. Rick Scott -- a top recipient of NRA donations who maintains an "A+" rating from the NRA's Political Victory Fund -- and the Senate Leadership Fund, a group focused on defending Republicans' majority in the Senate.

But after Wednesday's massacre at Marjory Stoneman Douglas High School in Broward County, Florida, Hoffman issued an ultimatum to Republicans.

According to the Times, the GOP donor pledged "that he would not give money to Mr. Scott, who is considering a campaign for the Senate in 2018, or other Florida Republicans he has backed in the past, including Representative Brian Mast, if they did not support new gun legislation."

And he's not stopping there. Hoffman also said he plans to reach out to other top donors to convince them to join him in closing their checkbooks until Republicans step up to the plate.