ST. LOUIS -- A Ferguson city council member and former mayor who was the driving force behind the "I Love Ferguson" campaign amid the turmoil that followed the fatal police shooting of 18-year-old Michael Brown has died. He was 56.

City officials confirmed Brian Fletcher's death Sunday. City spokesman Jeff Small said Monday he didn't know the cause of death.

Fletcher served as mayor for six years starting in 2005. After a four-year break from politics, he was elected as a councilman in April.

Brown, who was black and unarmed, was killed by Ferguson officer Darren Wilson during a street confrontation Aug. 9, 2014. A St. Louis County grand jury and the U.S. Department of Justice declined to prosecute Wilson, but the shooting led to protests and were a catalyst in the national Black Lives Matter movement.

Fletcher was not an elected official at the time of the shooting, but within days, he and others launched the "I Love Ferguson" campaign, printing thousands of yard signs, coffee mugs and T-shirts to promote civic pride and generate money for businesses damaged in looting. All told, more than $130,000 was donated.

"During the most difficult time in our city's history, Brian worked tirelessly and selflessly to bring people together in the spirit of a shared love for our community," Ferguson Mayor James Knowles III said in a statement.

The Justice Department released a report in March highly critical of Ferguson's police and court practices. City leaders continue to negotiate with Justice officials toward a settlement, but Fletcher worried in a November interview provisions of the settlement could bankrupt the city.

But he applauded changes since the unrest, including municipal court reforms and efforts by police to ease tensions with residents. He was optimistic of the return of many businesses to Ferguson, and developments such as a 23-unit loft project.

"It's an exciting time," Fletcher said in November.

Funeral arrangements are pending. Fletcher is survived by his wife and two daughters.