Dometry Kresluv was the newly-appointed Latvian ambassador to the United States. While staying at a hotel in New York City, he was accompanied by bodyguards, since several Latvian exiles in New York City harbored a grudge against his government, and against him in particular. While in a bar in Central Park, he mistakenly received murderer Steven Leight's coat from a cloakroom attendant, which still had evidence in the pocket linking Leight to his wife's murder.
Kreslov returned to his hotel, brushing past Adrian Monk on the way. Barely, had he realized that he was wearing the wrong coat, then Leight, who had followed him to the hotel, cornered him in an elevator and shot him and his two bodyguards to death. Leight then switched the coats back and ran out of the hotel.
Based on a remark he had made in an Eastern European dialect just before he died ("This is not my coat"), overheard by Monk, the NYPD was able to track down Leight and arrest him for the murders.