CHICAGO (CBS) — Heading into the last weekend before the Chicago mayoral election, a grassroots, union-backed group has launched a digital ad campaign to try to stop candidate Lori Lightfoot.

The ads, produced by United Working Families, claimed Lightfoot failed to discipline several Chicago cops while she headed the police board. One of them, detective Dante Servin, shot and killed 22-year-old Rekia Boyd.

The group said Lightfoot and the police board let Servin retire and collect a pension instead of firing him.

“An officer who killed a black woman, an unarmed black woman now gets to go home and feed his kids,” said activist Rachel Williams. “Where as her family has to go through the trauma, seven years after, and still does not see justice.”

United Working Families is backed by the Service Employees International Union (SEIU) and the Chicago Teachers Union. Both endorsed Preckwinkle.

Lightfoot’s campaign said she increased discipline of cops while on the police board and pointed to lax discipline in the police accountability report.

In a statement, a representative for Lightfoot’s campaign said:

“Lori is committed to holding officers accountable. Because he resigned on the eve of an evidentiary hearing before the Police Board, Lori did not have the opportunity to recommend firing Dante Servin or eliminating his pension. Servin went through a criminal case and an internal investigation long before the case got to the Police Board. Once the case got to the board, it moved and was set for an evidentiary hearing, and Lori even requested a change of location to allow more public access to the hearing. Servin resigned the day before the hearing was scheduled to occur, meaning he got to keep his pension. Before Lori was president of the Police Board, cases often got delayed for years, meaning officers were not held accountable for their actions and systemic issues in CPD persisted. When Lori was president, she consistently and aggressively challenged investigative bodies to bring cases to the board without unnecessary delays.”

CBS 2 is clarifying information from a Thursday night candidates forum. Toni Preckwinkle appeared to be a no-show at the forum Thursday evening sponsored by the West Side NAACP.

In fact, that’s what CBS 2 reported last night. But CBS 2 learned Friday that Preckwinkle’s staff told the NAACP more than two weeks ago that she had a scheduling conflict and would not be able to attend.

Yet the organization kept this information from CBS 2 and the community.

If you still haven’t decided who will get your vote in this historic run-off, you can study up on both candidates on our website. Head to CBSChicago.com/voterguide where you can read bios, and interviews, and see where both women stand on key issues.