CLAYTON, Mo. (AP) — On the fifth anniversary of Michael Brown's death in Ferguson, his father is urging the top St. Louis County prosecutor to reopen the investigation into the white police officer who fatally shot the black and unarmed 18-year-old.

Michael Brown Sr. spoke Friday outside the St. Louis County Justice Center.

"Justice has not been served," Brown, 41, said as he was surrounded by about three dozen supporters. "My son deserved to live a full life. But a coward with a badge ... chose not to value his life.

"My son was murdered in cold blood, with no remorse and no medical treatment."

Prosecuting Attorney Wesley Bell, St. Louis County's first black prosecutor, took office in January after his stunning defeat of seven-term incumbent Bob McCulloch.

McCulloch drew criticism for his handling of the investigation into the Aug. 9, 2014, shooting. Detractors accused McCulloch of guiding the grand jury to its decision, announced three months later, not to indict Darren Wilson.

The U.S. Department of Justice under then-President Barack Obama also declined to charge Wilson, who resigned in November 2014.

In a statement to The Associated Press, Bell would not say if the case may be reopened but said his office "is doing everything we can to understand the underlying issues that contributed to the tragic death of Michael Brown."

The statement said Bell's office is working with police "to implement policies and reforms that meaningfully address those issues, and help this community and this region heal."

Bell also is forming a special unit within his office to look at officer-involved shootings and potential cases of wrongful convictions.

Brown's mother, Lesley McSpadden, also has urged Bell to reopen the case.

Later Friday, a few hundred people gathered for a memorial service on Canfield Drive at the shooting site. The service included 4 1/2 minutes of silence, a symbolic reference to the 4 1/2 hours Brown's body remained on the street after the shooting.

Brown and a friend were walking down the middle of Canfield Drive in 2014 when Wilson told them to move to the sidewalk. An exchange of words led to a fight inside Wilson's SUV. Brown got out and began to ran, then turned around to face the officer.

Wilson told investigators that he shot Brown — who was 6 feet, 4 inches tall and 290 pounds (131 kilograms) — in self-defense. Some people in the Canfield Green apartment complex near the shooting initially claimed Brown had his hands up in surrender, but the grand jury found no evidence to confirm that.

The shooting led to weeks of protests that included looting and violent confrontations between demonstrators and police officers, many in riot gear and with military-style weapons. Protests escalated again after the grand jury announcement on Nov. 24, 2014. Wilson resigned days after the announcement.

While the Justice Department declined to indict Wilson , it issued a report citing racial prejudice in the Ferguson Police Department and a municipal court system that made money through court fines and legal fees, costs largely borne by black residents. A consent agreement signed in 2016 requires significant reforms.

Bell, 44, is among a wave of progressive prosecutors elected in recent years. His office seeks alternatives to incarceration when possible, such as some non-violent drug crimes. He has ended prosecution of most marijuana possession cases and reduced use of cash bail.

Bell would face no restrictions in re-examining Brown's death for potential murder charges. Wilson was never charged and tried, so there is no double-jeopardy. There is no statute of limitations on filing murder charges.

It would be unusual for a prosecutor to reopen an old case that's been so thoroughly examined, but not unheard of. A Philadelphia prosecutor initially declined to charge actor Bill Cosby with sexual assault, but a new prosecutor was elected and Cosby was charged and convicted.

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