Klobuchar was scheduled to speak at St. Louis Park High School in suburban Minneapolis ahead of Tuesday’s Minnesota primary, which she is fighting to win and notch her first victory. But dozens of protesters entered the gymnasium, raised signs and chanted “black lives matter” and “Myon,” a reference to Myon Burrell, who was convicted of the murder of 11-year-old Tyesha Edwards.

An Associated Press investigation questioned Klobuchar’s handling of the 2002 case, in which Burrell was sent to prison for life following a police investigation some say was flawed. Klobuchar has said if there is new information in the case it should be considered — a response that some activists have said doesn’t go far enough.

Klobuchar has struggled to win support from black voters, a major problem for her campaign as she seeks the Democratic nomination.