The Rev. Al Sharpton hopes the Michael Brown case will help change the way police engage the African-American community in this Missouri community and elsewhere.

“Michael Brown is going to change this town,” he told a massive crowd that clapped and shouted in response at Sunday services.

Hundreds filled the pews of Greater Grace Church. More crowded into the foyer, and hundreds remained on the parking lot unable to enter, all in a show of support for the African-American teenager who was shot by a police officer Aug. 9.

Rev. Sharpton announced a future march in Washington on policing. He criticized the militarization of police, saying they have acted in Ferguson as if they are “at war with … citizens.”

He urged the crowd to start showing up at the polls to vote and make a difference.

“Nobody can go to the White House unless they stop by our house,” he said. “We’ll be here until justice is achieved.”

In addition to Rev. Sharpton, Capt. Ronald S. Johnson of the Missouri Highway Patrol, who took charge of security operations in Ferguson last week, also was on hand to offer support to the slain youth’s family, as was U.S. Rep. William Lacy Clay, D-St. Louis.

“I want you to know these parents are not going to cry alone, they’re not going to stand alone,” Rev. Sharpton said in speaking of the teen’s parents who were also at the church. “We’ve had enough.”

Benjamin Crump, the Brown family’s lawyer, also took the podium.

“We’re here to talk about justice,” said Mr. Crump. “We’re here to stand up for our children, because if we don’t stand up for our children, nobody will stand up for our children. They just want what anyone else would want if their child was shot in broad daylight.”

When Capt. Johnson of the Highway Patrol spoke he compared the dead teen to his own son.

“When this is over, I’m going to go into my son’s room, my black son, who wears his pants sagging, wears his hat cocked to the side, got tattoos on his arms. But that’s my baby,” Capt. Johnson said. “Michael is going to make it better for our sons, so they can be better men.”

Mr. Crump told supporters not to lose focus amid news that the teen is alleged to have robbed a convenience store just before the shooting. He called the allegations an attempt to assassinate the teen’s character.

Rev. Sharpton came in with the Brown family, who received a standing ovation. The teen’s mother, Lesley McSpadden, overwhelmed by the response, bowed her head, breaking down in tears.

As at previous forums, Rev. Sharpton urged demonstrators protesting Michael Brown’s death to do so in a peaceful manner.

He also urged Ferguson residents to take to the streets with bright yellow T-shirts, calling themselves “Disciples of Justice,” or DJs, to help contain any violence on the streets.

But not everyone was happy with Rev. Sharpton’s speech.

“He always wants to hush us without handling the whole situation,” said Zsazzi Powell, 27, a stay-at-home mother in Ferguson. “We’re tired of all the pacifying.”