Serena Williams had a meltdown — that cost the tennis ace a match on a conduct violation — after an unusual call at the U.S. Open on Saturday, Yahoo! Sports reports.

Serena berated an official and lost a match to Kim Cjisters from Belgium during their Women’s Semi-Final US Open match at the USTA Billie Jean King National Tennis Center in New York over the weekend — the judge claims the Grand Slam champ threatened to kill her following a dispute over a call.