FERGUSON, Missouri (CNN) - We're with you.
That's the message Attorney General Eric Holder says he delivered to the people of Ferguson, Missouri, when he visited Wednesday to check in on the federal civil rights investigation into the shooting of unarmed black teenager Michael Brown by a white police officer.
"This attorney general and this Department of Justice stand with the people of Ferguson," he told reporters Thursday in Washington.
Holder has assigned scores of FBI agents and Justice Department investigators to look into Brown's August 9 death in the suburban St. Louis city.
Police have said Brown and the officer, Darren Wilson, struggled over the officer's gun; witnesses who have spoken publicly say the 18-year-old had his hands in the air when he was shot.
A St. Louis County grand jury began hearing testimony in the case Wednesday, but it's not expected to make a decision on charges against Wilson before mid-October.
While Holder said agents have made "significant progress" in their investigation, he said it will still take time to complete and asked for the community's support.
"The people of Ferguson can have confidence in the federal agents, investigators and prosecutors who are leading the process," he told reporters Thursday in Washington. "Our investigation will be fair, it will be thorough and it will be independent."
"On a personal note," the African-American father of a teenage son told reporters, "I've seen a lot in my time as attorney general, but few things have affected me as greatly as my visit to Ferguson."
Holder met with Brown's family not long after the teen's mother viewed her son's bullet-riddled body at a morgue for the first time. He heard from a woman who said her brother died in an encounter with Ferguson police in 2011. And he spoke to the community of a festering mutual mistrust between law enforcement and many communities in the United States.
"I wanted the people of Ferguson to know that I personally understood that mistrust," he said.
His trip was not universally well-received, however.
Activist Akbar Muhammed gave the attorney general low grades for the trip.
"We thank him for coming, but he gets a D minus," Muhammed said.
"He came to have a community meeting, and in that community meeting he didn't meet with any of us who were out in the street," he said.
For the first time since Brown was fatally shot, streets emptied out early Thursday.
The evening before, protest crowds thinned from hundreds to dozens, then disappeared. Thunderstorms in the Missouri town may have doused their numbers.
Late Wednesday, police made targeted arrests. Earlier in the day, they suspended an officer caught on video pointing a semiautomatic rifle at peaceful protesters and shouting profanities at them the night before.
A small hubbub arose when protesters held up signs supporting the officer who shot Brown. One read: "Justice for Police Officer Wilson."
Other protesters argued with them heatedly, then police whisked them away.
But Wednesday was so peaceful that state troopers had time to go buy a basketball for neighborhood youths and a net for their goal, which they installed, Missouri State Highway Patrol Capt. Ron Johnson told reporters.
Before he spoke, a chaplain prayed, thanking God for a night "better than all the nights we've had before."
Slow wheels of justice
The grand jury meeting in Clayton, Missouri, will examine whether charges should be filed against Wilson in Brown's death.
St. Louis County Prosecutor Bob McCulloch told local media Wednesday that the grand jurors will see every bit of evidence that investigators gather and will be allowed to meet as long as they want before making a decision.
"The aspirational time is by mid-October to have everything completed," he told CNN affiliate KMOV.
He wants the case to proceed through the grand jury "expeditiously" but also "thoroughly," he said. "We're not going to rush it through, and we're not going to leave anything out."
On Thursday, Holder declined to answer questions about whether the department was looking into past allegations of abuse by the department, including a 2009 incident in which a man said police bloodied him in a jail cell, as well as the 2011 death that Holder spoke of.
"I'll just say at this point, we are keeping all of our options open," he said.
Controversy over prosecutor
On Thursday, activists delivered petitions they said were signed by 70,000 people asking McCulloch to step down.
"That is the only way we're going to bring strong confidence within this investigation," Missouri state Sen. Jamilah Nasheed said.
Critics have complained that McCulloch, who is tasked with prosecuting Wilson, could be biased in the officer's favor. McCulloch comes from a family of law enforcement officers.
His father was killed in the line of duty.
McCulloch has rejected that criticism, telling St. Louis radio station KTRS on Wednesday that the experience of losing his father turned him into a passionate advocate for all victims of violence.
He said again Thursday after the petitions were delivered that he would not step aside.
"I appreciate and understand the concerns of those who honestly believe that I cannot or will not be fair to all in the gathering and presentation of the evidence pertaining to the tragic death of Michael Brown," he said in a statement. "Although I understand the concerns, and do not take lightly the demands that I recuse myself from this case, I also recognize that I have a responsibility to the family of Michael Brown, the people of Ferguson and the entire community."
On Wednesday, he blasted Missouri Gov. Jay Nixon for his response to the controversy. Nixon had said he would not ask McCulloch to recuse himself, saying he found that it would disrupt the established process.
McCulloch's response: Nixon needs to "man up" and remove him, if he thinks it's the right thing to do.
The state of emergency the governor declared Saturday gave him the authority to do so, if he sees fit, McCulloch told KTRS.
Nixon may have the option of installing a special prosecutor.
That would be a good idea, said Antonio French, a St. Louis alderman who has been a protest fixture. The African-American community doesn't trust McCulloch, he said, or law enforcement in general.