Hillary Clinton met privately Monday evening in Chicago with the families of young black people who were killed by police officers, according to her campaign, as the Democratic front-runner pushes forward her plan for criminal justice reform.

The participants included Lesley McSpadden, the mother of Michael Brown, whose death tipped off unrest in Ferguson, Missouri, last year, and Sabrina Fulton, the mother of Trayvon Martin, who was killed by a neighborhood watchman in Florida in 2012.

Also in attendance was Samaria Rice, the mother of Tamir Rice – the 12-year-old killed by police in Ohio while he was holding a toy gun last year – and Maria Hamilton, the mother of Dontre Hamilton, the mentally ill man who was killed by a police officer in Milwaukee in 2014.

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Clinton mostly listened to the mothers’ stories, according to a campaign aide, who said the meeting was meant to address the distrust between police officers and minority communities.

Criminal justice reform has become a key pillar of Clinton’s campaign as she seeks to appeal to black voters – a key Democratic voting bloc, especially in the South, where Clinton strategists feel confident they can outperform their chief rival for the nomination, Vermont Sen. Bernie Sanders.

Last week, the former secretary of state added several new planks to her criminal justice reform platform. They include “banning the box” that prospective employees are asked check on job applications if they were arrested; a call for legislation to end racial profiling in policing; and an end to the sentencing disparity between crack and powder cocaine. Previously, she called for an end to the “era of mass incarceration.”

The campaign aide also said that Monday’s meeting was meant to emphasize the epidemic of gun violence in America, an issue that has become central to Clinton’s campaign and a wedge she has used against Sanders.

Clinton’s emphasis on criminal justice reform comes at the same time as President Obama pushes the issue. “Pretty much up and down the line, what we see is disparities in how white, black, Hispanic suspects are treated,” Obama told ”NBC Nightly News” anchor Lester Holt on Monday. “Higher arrest rates, tougher sentencing, longer sentences.”

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Clinton visited a black church in June near Ferguson, where she spoke about the need to confront deep unresolved issues of race. Last week, her campaign kicked off an effort dubbed “African Americans for Hillary” in Atlanta with Rep. John Lewis, a leader of the civil rights movement, and other prominent black leaders.

Speaking later that day at Clark Atlanta University, a historically black college, Clinton connected her call for criminal justice reform to race. “We also need to look beyond the specific criminal justice reforms to the deep-seated social and economic inequities that divide our country,” she said. “More than half a century after Rosa Parks sat and Dr. King marched and John Lewis bled, race still plays a significant role in determining who gets ahead in America and who gets left behind.”

Correction: An earlier version of this story stated that Clinton met with the families of young black men killed by police violence. In fact, her meeting included the families of female victims as well.