Lezley McSpadden, mother of Michael Brown, who was killed in Ferguson, Mo., on Aug. 9, 2014, bows her head in prayer. (Shannon Stapleton/Reuters)

The mother of Michael Brown, the 18-year-old whose 2014 shooting by police in Ferguson, Mo., ignited protests that lasted for weeks, is backing Democrat Hillary Clinton.

Clinton's campaign announced the endorsement Tuesday as voters began casting primary ballots in Missouri, one of five states voting on what could be a decisive day for Clinton. She has appeared to lose ground in Missouri to Sen. Bernie Sanders of Vermont, with the most recent poll showing an effective tie.

"When I lost my son, I lost my world. 'Big Mike' was a big boy, but he was my baby boy; my only child, and his life was brutally taken from me," Lezley McSpadden wrote in her endorsement statement.

"Parents are not supposed to bury their children, especially by murder. But the reality is, that far too many black parents have; not just by senseless gunfire but by lawful gunfire. Enough is Enough."

McSpadden was among a group of African American mothers who met privately with Clinton last year. All had lost children to violence, and some have gone on to campaign for Clinton in states with significant African American populations.

Clinton has made the mothers' stories a regular part of her political speeches, as she talks about the need for criminal justice reform and better gun control. She has called for mandatory body-worn cameras for police officers, something McSpadden is advocating in Missouri. She testified before the state legislature last month in favor of a bill to require cameras that could capture police interactions with civilians.

Clinton has won lopsided victories in Southern states on the strength of her support among black voters. But she suffered a surprise loss in Michigan last week when a strategy that leaned heavily on the state's share of black voters fell short. Sanders made inroads among black voters there, and he has said he can do the same elsewhere.

McSpadden praised Clinton's "realistic proposals" on health care, housing, education and other issues, and she said Clinton is "the candidate most likely to achieve the task of working across party lines to get needed legislation passed."

McSpadden did not mention the Missouri primary in her statement or specifically ask others to vote for Clinton on Tuesday. She also did not mention Clinton's rival, Sanders, although her reference to "realistic" Clinton policy positions echoes Clinton's critique that Sanders's ideas are far-fetched and too expensive to stand a chance in Congress. McSpadden also appeared to make references to the Republicans running against Clinton and to President Obama, whose legacy Clinton regularly tells African American audiences she will protect.

"This election season, we are at battle for the soul of our nation," McSpadden said. "If we want to continue to build on the progress made by our country, we need a president who is ready to lead — and I trust Hillary Clinton."

Brown, who was unarmed, was killed Aug. 9, 2014, by a white officer, Darren Wilson. The shooting led to sometimes violent street protests in Ferguson, a St. Louis suburb with a history of tensions between police and black residents. A grand jury declined to indict Wilson, which led to further protests.

Last month, the Justice Department sued the city, alleging that, 18 months after Brown's death, police and the court system continue to violate black residents’ civil rights.

The suit alleges “ongoing and pervasive” violations arise from the city’s use of law enforcement to generate revenue, often from court fines.