U.S. Rep. Christopher Collins, the upstate Republican congressman and early supporter of President Donald Trump, reportedly resigned his office Monday after court documents showed he expected to plead guilty in a federal insider trading case involving his son and another co-defendant.

Collins, who pleaded not guilty to a superseding indictment earlier this month, is expected to enter his change of plea Tuesday afternoon in a Manhattan courtroom, with his son Cameron and Stephen Zarsky to follow on Thursday.