After four nights of confrontations between police and residents of Ferguson, President Barack Obama went on television Thursday and appealed for peace and calm on the streets of the Missouri town.

The circumstances of the death of Michael Brown, the 18-year-old unarmed man shot by a police officer on Saturday in an incident that sparked looting, vandalism and protests, are "heartbreaking and tragic," he said.

Obama, speaking while on vacation on Martha's Vineyard in Massachusetts, said there is no excuse for violence against police or excessive force against peaceful protesters.

It was a carefully worded statement that also called for transparency in the investigation "to see that justice is done."

There was no specific mention of the racial tensions flaring in Ferguson — a mostly black town patrolled by a mostly white police force. "Let's remember we are part of one American family," Obama said, without referring to race.

The unrest in Ferguson has put another racially charged controversy on the White House doorstep for the country's first black president. Obama's words and his actions are under scrutiny and questions were raised in the days after the shooting about his response.  

Obama had issued a written statement on Tuesday that offered condolences to the Brown family and urged Americans to comfort each other. There was some criticism on social media noting that a statement came first from the president on the death of actor Robin Williams on Monday.

The White House had an optics problem and took some flak on Wednesday night when deputy press secretary Eric Schultz wrote on Twitter about Obama attending a birthday party.

"A good time was had by all," he wrote.

Meanwhile in Ferguson, tear gas was being fired at protesters and a camera crew by heavily armed police in military-style riot gear and two reporters were detained while filing their stories at a McDonald's.

Stronger response warranted?

White House officials said Obama was briefed about the violence Wednesday night after the party, and he was updated again Thursday morning before making his statement. He ordered the FBI and Department of Justice to get involved, and spoke by phone to Missouri Gov. Jay Nixon.

It's not clear whether the changes to police tactics announced later in the day by Nixon were a direct result of that conversation.

William Cobb, an associate professor and director of the Institute of African American Studies at the University of Connecticut, was in Ferguson earlier this week to witness the events there, and listened carefully to Obama's statement.

Police Shooting Missouri

The death of teenager Michael Brown has caused clashes in the streets of Ferguson, Mo., including this one Wednesday. (Jeff Roberson/The Associated Press)

"I thought the president's comments were middle of the road. Understandably, there are constraints on his position. But what we saw here, it looked like a siege in an American city. I think what has happened warranted something that was at least a little bit stronger from the president," said Cobb.

There could be several reasons Obama didn't go further in his remarks, Cobb said, including that he may not want to make the story about him and wanted to keep the focus on Missouri. The investigations are ongoing and Obama, a lawyer before he was a politician, may also be conscious of jeopardizing them by weighing in with his opinions.

"It also might just be his own cautious style," said Cobb. "I don't know what it ultimately is but I think the net effect is something that was perhaps more neutral than it should have been."

That Obama didn't mention racial tension came as no surprise to Cobb, because he said Obama generally avoids the issue.

"Even dating back to his candidacy he was reluctant to discuss race unless it was pressed upon him and I think this fits into that template," he said.

But when Florida teen Trayvon Martin was killed, Obama did discuss race, and he made it personal. The unarmed 17-year-old from Florida was shot by George Zimmerman, a neighbourhood watch patrol volunteer, in 2012. 

"If I had a son, he would look like Trayvon," the president said a few weeks after the shooting. More than a year later, soon after Zimmerman was found not guilty of second-degree murder, Obama spoke at length about race in America and his own personal experiences.

Obama has to be careful

"Trayvon Martin could have been me 35 years ago," Obama said. Americans need to do some "soul-searching," he added.

That was one of the few times Obama has inserted himself into conversations about race in the U.S., and he was criticized by some for doing it.

He also faced a backlash after one of the other occasions, early on in his presidency when a black Harvard professor, Henry Louis Gates Jr., was arrested by a white police officer at his own home and charged with disorderly conduct. Obama, who is friends with Gates, said police acted "stupidly." Days later, when more facts were known about the incident, the president conceded his remarks likely inflamed the situation.

The country's first black president has had to learn how to navigate his role in sensitive racial matters and likely accept how difficult it is to do that in a way that will satisfy everyone.

Cornell William Brooks, president of the National Association for the Advancement of Colored People, told The Associated Press he understands that Obama has to walk a fine line with the situation in Ferguson.

"The president as the chief executive has to be careful and thoughtful in his choice of words, particularly at a moment when there's unrest — unrest in the streets, but also unrest in the American conscience," Brooks said.

Cobb suggested there may be some "fatigue" on the president's behalf.

Michael Brown isn't the only recent case of a black man dying after a confrontation with police. Eric Garner died last month after being put in a chokehold by an officer in New York.

"I think there are a lot of people from the Oval Office down who have fatigue in dealing with this over and over again," he said. "At some point I think it becomes difficult for people to emotionally process what it is that we're seeing and that we're back in the same place again and again and again."