Troubled singer Britney Spears (here with her son Sean) hit a new low, when she called up ex-husband Kevin Federline, threatening to kill herself by driving off a cliff. Spears told Federline that she was going to ?kill herself? and that he was to be blamed for it. ?I'm going to drive off the cliff! It?s going to be your fault that I killed myself,? News of the World quoted her as telling Federline. After giving him the ultimatum, the Toxic star sped down Los Angeles? famous Mulholland Drive, that runs along a steep road. The drama occurred shortly after a judge ruled that her sons can stay with her once a week. During the court hearing, while Britney faced the judge in her children?s custody hearing, Federline spent time shooting scenes for episode seven of his guest spot on TV show One Tree Hill. After the shoot, Federline partied at a club like a rock star in the VIP area, ordering up rounds, people.com reported.