WASHINGTON -- President Barack Obama urged calm across the nation on Monday in response to the decision by a grand jury not to indict Darren Wilson, the Ferguson police officer who killed unarmed black teenager Michael Brown in August.

In brief remarks at the White House, the president acknowledged that anger is "an understandable reaction" to the news that Wilson was let go without being indicted. Still, he said, the jury's decision carries "the rule of law" and people must accept it.

"I join Michael's parents in asking anyone who protests this decision to do so peacefully," Obama said. "Let me repeat Michael's father's words: 'Hurting others or destroying property is not the answer. No matter what the grand jury decides, I do not want my son's death to be in vain.'"

The president's plea for nonviolence came just after St. Louis County prosecutor Robert McCulloch announced that members of the jury reached their decision after meeting for 25 days and hearing more than 70 hours of testimony from more than 60 witnesses.

Brown's Aug. 9 death sparked protests in Ferguson, a St. Louis suburb, and sparked a national debate on the relationship between law enforcement and young black men. On Monday night, police in Ferguson and in cities around the country braced for more protests and possible violence in response to the grand jury's decision.

Obama acknowledged the deeper issues underlying the situation, namely the feeling that laws are often applied in a discriminatory fashion against people of color.

"What is also true is that there are still problems, and communities of color aren't just making these problems up," he said.

The president added that the nation has made "enormous progress" when it comes to dealing with race relations -- something he personally can attest to.

"I have witnessed that in my own life," he said. "To deny that progress, I think, is to deny America's capacity for change."