Mayor Walsh's appointment of William Gross as the first African-American police commissioner in Boston represents a breakthrough some observers say was a long time coming.

The son of a single mother, Gross acknowledged he was making history for a whole generation of young people.

“It shows that any kid in Boston that they will have the opportunity to be mayor or commissioner or chief, if we all work together,” Gross said at a July 23 news conference, where Bill Evans announced his retirement as commissioner to take a job at Boston College.

Gross, 54, started out as a street cop in 1985. Thirty-three years later, he’ll lead police in a city with what he called a "negative history." He pointed to violent protests against school desegregation in the 1970s. In those early days, the concerns over racial tensions kept his mother up at night.

“Many calls from my mother worried because of the atmosphere at the time,” Gross said. “The community and Boston police. But, if you want change, be change. That’s why I became a police officer.”

Larry Ellison, president of the Massachusetts Association of Minority Law Enforcement Officers, graduated from the police academy with Gross in the 1980s.

“It is a big deal, if you know Boston,” Ellison said. He pointed to Boston’s first African-American police officer, Horatio Homer, who joined the force a century ago.

“A hundred years since his appointment to now we have our first black police commissioner,” Ellison said.

Roughly 30 percent of the department's 2,200 sworn officers are of color.

“I definitely think it’s something we have to work on,” Ellison said. “I mean representing police officers of color--t has not always been easy. I think that we will have agreements and disagreements with the new police commissioner Gross.”

Gross has his work cut out for him. The number of homicides in the city has been increasing in recent years.

“One homicide's too much, one senseless act of violence too much,” Gross said. “We’re going to walk towards each other, so we can step forward and overcome any obstacle we face in this city.”

Gross believes a strong bond between police and community will make that happen.

This story has been updated.