Kevin Federline is sharing his side of one of Britney Spears' most viral moments. In his upcoming new tell-all, You Thought You Knew, Kevin looked back on the time his pop star ex shocked the world by shaving her head. This was in 2007 amid their divorce, so he had a front row seat. In an excerpt obtained by E! News on Thursday, Kevin alleged the singer had checked herself out of rehab and "showed up at the gate" of his Tarzana, California home, "ringing the bell and shouting a bunch of things that didn't make sense." He wrote: "The only words that came through clearly were: LET. ME. IN.