The suspect arrested after the second assassination attempt on former President Donald Trump reportedly had been flagged previously for erratic behavior concerning Ukraine.
Ryan Wesley Routh, 58, faces charges of possessing a firearm despite being a convicted felon and possessing a firearm with an obliterated serial number after an apparent assassination attempt on the former president Sunday at the Trump International Golf Club in West Palm Beach, Florida. Additional and more serious charges are possible as the investigation continues, and prosecutors seek an indictment from a grand jury.
The Wall Street Journal reported Monday that Routh alarmed people after he traveled to Ukraine hoping to join the fight against Russia shortly after President Vladimir Putin's forces invaded in 2022.
One nurse, worried about Routh's threats of violence after she encountered him in Kyiv, said she reported the man to a Customs and Border Protection officer at Washington's Dulles airport in June 2022.
Chelsea Walsh told the officer that Routh was among the most dangerous Americans she met during her six-week visit to Ukraine, WSJ reported.
Sarah Adams, a former CIA officer who helped run a network that linked 50 aid groups to share information and coordinate humanitarian and volunteer efforts, said Routh was known as a "fraudster" and "kind of a whack job," the outlet said.
In early June, aid groups banned Routh from their Signal Messenger groups, and reported his activities to the State Department. Adams said the groups were concerned Routh might be engaging in human trafficking or immigration fraud.
One French man, who said Routh helped secure him a spot in a Ukrainian army unit, added the American was angry at Trump.
"Ryan was very upset about the fact that Trump was trying to negotiate a deal with Putin instead of trying to really have Ukraine's back," said the man, who asked not to be identified.
The FBI learned of Routh in 2019, when a tipster said he had a firearm despite being a felon. However, when questioned further, the tipster wouldn't verify providing the information, a bureau official said Monday.
The New York Post reported Tuesday that Routh has a lengthy arrest record in Guilford County, North Carolina, where he was once a resident of Greensboro.
His county arrest record lists charges ranging from writing multiple bad checks to felony firearm possession, possession of a stolen vehicle and multiple counts of possession of a weapon of mass destruction in 2002, specifically, a "binary explosive with a 10-in[ch] detonation cord and a blasting cap."
The Associated Press contributed to this story.