A Russian-born, mafia-linked businessman whose ties to both Donald Trump and loyalists of Russian President Vladimir Putin have sparked scrutiny, visited Trump Tower last month for undisclosed business, he told POLITICO. The businessman, Felix Sater, also donated the maximum allowable contribution to Trump’s presidential campaign, according to the campaign’s most recent FEC filing.

Sater’s business relationship with Trump has been the subject of sworn testimony by both men and has come under scrutiny because of Sater’s past associations and the Trump campaign’s unusual stances on Russia. Sater was convicted for stabbing a man in a bar fight in the early '90s, and pleaded guilty to racketeering in 1998 for his role in a mob-orchestrated stock fraud, according to The Washington Post. His racketeering sentence was reduced for cooperating with American intelligence officials on undisclosed matters related to national security.