North Carolina police believe that the robbery that occurred at Greg Biffle's home just weeks after his fatal plane crash was committed by the late NASCAR driver's friends as part of a broader coverup, according to a sheriff's search warrant obtained by the Charlotte Observer. The incidents occurred on January 7 and January 8, nearly one month after Biffle's death at age 55. More than $30,000 in cash as well as guns and memorabilia were allegedly stolen from the residence.