OLYMPIA, Wash. » Two stepbrothers suspected of trying to steal beer from a grocery store were not armed with guns when they were shot Thursday by a police officer who confronted them in Washington state’s capital city, authorities said.

The officer reported he was being assaulted with a skateboard early Thursday before the shooting that left a 21-year-old man critically injured and a 24-year-old man in stable condition. Both were expected to survive.

The shooting, which is being investigated by a team of detectives from several agencies, prompted protests.

Hundreds of people turned out Thursday evening, rallying first at a park, then marching about a mile to a building that houses the Olympia police headquarters and City Hall. They chanted "Black Lives Matter," ”No Justice, No Peace" and the names of the young men who were shot.

"We’re not going to say this kind of violence is OK," one speaker, Rafael Ruiz, 32, told the crowd. "I’m here to defend the victims of the police shooting."

The stepbrothers are black, and the officer is white, but Olympia Police Chief Ronnie Roberts said, "There’s no indication to me that race was a factor in this case at all."

Demonstrators held signs that read "Race is a Factor" and "We Are Grieving."

Olympia police tweeted their thanks to marchers "for keeping the event nonviolent."

"We are committed to helping our community work through this difficult circumstance and help us understand this tragic event," the police chief told a news conference Thursday afternoon.

Brad Watkins, chief deputy of the Thurston County Sheriff’s Department, said two skateboards were recovered from the shooting scene and an investigation will likely take three to six weeks.

The two men were identified as Andre Thompson, 24, and Bryson Chaplin, 21, both of Olympia.

"It was terrible," the young men’s mother, Crystal Chaplin, told KIRO-TV. "It’s heartbreaking to see two of my babies in the hospital over something stupid."

Officer Ryan Donald was among those who responded around 1 a.m. to a call from a Safeway store, Roberts said. Employees said two men tried to steal beer and then threw the alcohol at workers who confronted the pair.

Officers split up to search for the men. Donald encountered two men with skateboards who fit witnesses’ descriptions, and moments later, he radioed in that shots had been fired, the police chief said.

In radio calls released by police, Donald calls dispatchers once he spots the men, and again to report that he fired shots.

"I believe one of them is hit, both of them are running," Donald said.

He tells dispatchers that one of the men "assaulted me with his skateboard."

"I tried to grab his friend," Donald said. "They’re very aggressive, just so you know."

He says he has one man, then both, at gunpoint and asks for help.

Seconds later, he shouts, "Shots fired! One down," and asks for more backup units. He then says the second man has been shot.

The police chief said Donald wasn’t injured but an officer "has the right to defend himself" if a suspect wields an object that could be used as a deadly weapon.

The shooting follows a string of high-profile killings of unarmed black men by police, including Michael Brown in Ferguson, Missouri, and Eric Garner in New York City, which set off weeks of protests and a national "Black Lives Matter" movement that has gained momentum across the country.

Donald, 35, who is on administrative leave pending the investigation, has been with the department for just over three years. No residents have filed complaints against him, and he was recently recognized by the agency for being proactive on investigations, Roberts said. He worked previously as an Army police officer, the chief said.

Olympia Mayor Stephen H. Buxbaum called for calm in the community.

"It deeply saddens me that we have two young people in the hospital as a result of an altercation with an officer of the law," he said. "Let’s come together to support their needs, the officer’s needs, the needs of the families and our community’s needs. Let’s not be reactive."

Merritt Long, a retired chairman of the state’s liquor control board, was one of several residents to attend the news conference Thursday.

"Does the punishment fit the crime?" he asked afterward. "Given the seeming epidemic of this happening not only here but in our country, it makes you pause and wonder what’s going on."