Germany's Jan-Lennard Struff has also withdrawn from the final Grand Slam of the year.
The ABC said the man had pointed a long-barrelled gun at Kyrgios's mother Norlaila and demanded the keys to a green Tesla.
Karen Khachanov stood on court, arms raised, basking in a rowdy crowd’s cheers after reaching his first Grand Slam semifinal at the US Open.
Kyrgios, Wimbledon finalist this year, has recorded the most wins on tour since the end of the French Open and continued the finest season of his career with a 7-6(11), 3-6, 6-3, 6-2 victory over Medvedev in a blockbuster fourth-round clash.
Medvedev cruised into the fourth round with a straightforward 6-4, 6-2, 6-2 victory over Chinese qualifier Wu Yibing.
In a statement released by her solicitors on Tuesday, Anna Palus said the 27-year-old Australian had defamed her by making "a reckless and entirely baseless allegation."
Taylor Fritz blasted his way to a 6-3, 6-2 win over Australian Nick Kyrgios while Cameron Norrie fought back to beat former world No. 1 Andy Murray 3-6, 6,-3 6-4 in an all-British clash.
Kyrgios launched a dozen aces on the way to a 6-4, 6-3 win over his Japanese opponent to claim his first singles title since winning the same hardcourt tournament in 2019.
The Serb beat the Australian in four sets, 4-6 6-3 6-4 7-6(3), to emerge the champion.
The top seed overwhelmed Britain's Cameron Norrie 2-6 6-3 6-2 6-4 in the second semifinal.