The Republican received an enveloped with a photo of himself bruised and bandaged. Next to Paul's face on the image include a gun to his head with the words: "I'll finish what your neighbor started you motherf----r."
In a statement on Monday, Paul addressed the package and the threat, according to Fox News.
"I take these threats immensely seriously," Paul wrote. "I have been targeted multiple times now, it is reprehensible that Twitter allows C-list celebrities to advocated for violence against me and my family."
"This must stop. Just this weekend Richard Marx called for violence against me and now we receive this despicable powder-filled letter," he ended.
Paul was referring to singer and songwriter Richard Marx, who tweeted on Sunday: "I'll say it again: If I ever meet Rand Paul's neighbor I'm going to hug him and buy him as many drinks as he can consume."