The music festival Summerfest is investigating after a performer, Lizzo, said a security guard "tackled and attacked" her team after a performance in Milwaukee. (CNN) - The music festival Summerfest is investigating after a performer, Lizzo, said a security guard "tackled and attacked" her team after a performance in Milwaukee on Thursday night. The rising star tweeted about the incident, saying a guard "slapped and manhandled my hair stylist and stylist." When asked about the investigation and the security guard, Summerfest did not give any additional information. The festival tweeted the same statement Thursday night.