(AP) -- Calling for understanding in the face of racially charged anger, President Barack Obama said Monday that the vast majority of protesters in a St. Louis suburb were peaceful, but warned that a small minority was undermining justice for the unarmed black man shot and killed by police.

During a brief pause in his summer vacation, Obama expressed sympathy for the "passions and anger" sparked by the death of 18-year-old Michael Brown in Ferguson, Missouri, but said giving in to that anger through looting and attacks on police only stirs tensions and leads to further chaos. He said overcoming the mistrust endemic between many communities and their local police would require Americans to "listen and not just shout."

"That's how we're going to move forward together, by trying to unite each other and understand each other and not simply divide ourselves from one another," Obama told reporters at the White House.

Obama said Attorney General Eric Holder would travel to Ferguson this week to meet with FBI and other officials carrying out an independent federal investigation into Brown's death. He said he also had told Missouri Gov. Jay Nixon he wanted to ensure the use the National Guard in help calm tensions in Ferguson must be limited in scope, and said he would be monitoring that operation in the coming days to see whether the guard's involvement was helping or hurting.

Obama also weighed in for the first time publicly on the militarization of some local police departments, saying it probably would be useful to examine how federal grant dollars had been used to allow local police to purchase military-style equipment, an issue that's come to the forefront amid the violent protests in Ferguson. Obama said the distinction between the military and domestic law enforcement was one of the great things about America.

Appearing in the White House briefing room in a dress shirt but no tie, Obama also spoke for the first time to the racial tensions and grievances perceived by African-Americans in Ferguson. In previous comments about the situation, Obama had avoided talking directly about race, wary of rushing to judgment or further inflaming the situation.

Weighing his words carefully, Obama said it was clear that disparities in how blacks and whites are treated and sentenced must be addressed, calling for more safeguards and training to prevent missteps. At the same time, he acknowledged the difficult situation that police officers sometimes face.

"There are young black men that commit crime. We can argue about why that happened -- because the poverty they were born into or the school systems that failed them or what have you-- but if they commit a crime, then they need to be prosecuted," Obama said. "Because every community has an interest in public safety."

Obama's remarks on the crisis were the first since the situation in Ferguson escalated over the weekend, with Nixon, the Missouri governor, ordering a midnight curfew for Ferguson and ordering the National Guard to help restore order. Nixon lifted that curfew on Monday, but tensions remained high the morning after police once again deployed tear gas in response to what they said were reports of gunfire, looting and vandalism by protesters.

The ongoing confrontation, with military-style vehicles rolling through suburban streets, has left citizens across the country wondering how such a war-like scene could play out in America's heartland.

Shortly before speaking to reporters Monday, Obama received an update from top advisers including Holder and White House Counsel Neil Eggleston. Obama has asked the Justice Department and FBI to investigate Brown's death, and Holder over the weekend ordered a federal medical examiner to perform a third autopsy on Brown.

Obama weighed in on the crisis during a brief break in his annual summer vacation at Martha's Vineyard, where the president was spending two weeks with his family while juggling multiple crises in the U.S. and overseas. Obama returned to the White House late Monday and planned to return to the Massachusetts island on Tuesday. His brief return to Washington had been announced by the White House before the standoff in Ferguson began.

Brown was unarmed when he was fatally shot by a police officer on Aug. 9 in Ferguson, a predominantly black community that long has been at odds with the mostly white police department. Results of an independent autopsy released Monday by Brown's family determined that Brown was shot at least six times, including twice in the head.