Mingus' temper was notoriously bad, and he twice hit Knepper. Once, while onstage at a memorial concert in Philadelphia, Mingus reportedly attempted to crush the hands of his pianist, Toshiko Akiyoshi, with the instrument's keyboard cover, then punched Knepper. Later, Mingus reportedly punched Knepper in the mouth while the two men were working together at Mingus's apartment on a score for Epitaph, in preparation for what became his disastrous concert at New York Town Hall, on October 12, 1962. The blow broke one of Knepper's teeth, ruined his embouchure and resulted in the loss of the top octave of his range on the trombone for almost two years. This attack ended their working relationship and Knepper was unable to perform at the concert. Charged with assault, Mingus appeared in court in January 1963 and was given a suspended sentence. According to his daughter, Robin, Mingus also later mailed heroin to Knepper's home, and made an anonymous phone call to the police. A little girl at the time, she remembers the police questioning her father after the mailman delivered the package. Nevertheless, in the 1970s, the two eventually reconciled thoroughly enough to play together in concert and on at least one of Mingus' last albums.