FARGO, N.D. >> A gunman opened fire on police and firefighters “for no known reason” as they responded to a traffic crash in North Dakota, killing one officer and wounding two others before another officer killed him, Fargo’s police chief said Saturday.

A 25-year-old woman was also injured in the shooting Friday afternoon, but authorities did not say who shot her. The gunman did not hit any firefighters, Chief David Zibolski said, but a fire truck was struck by gunfire.

Zibolski identified the shooter as Mohamad Barakat, 37, of Fargo, but provided few details about him or the shooting, citing officials’ desire to protect the investigation. He said he was confident authorities would eventually determine the motive.

“The first thing we always want to know in a situation like this is, ‘Why?’” he said. “Why would somebody do this? What happened?”

Authorities were investigating what Zibolski called a “routine traffic accident” on a busy Fargo street when Barakat opened fire. He did not appear to have been involved in the crash police were working, Zibolski said.

Among the drivers who witnessed what happened was Chenoa Peterson. She told The Associated Press on Saturday that the shooter appeared to have ambushed the officers. The gunman was at the rear of a car in a bank parking lot near the traffic crash when he fired on an officer not more than 20 feet (6 meters) away, she said.

“He was holding up the trunk of the car with his arm, and then I see the gun come up, and he set it on his shoulder and just pointed it directly at an officer in front of him,” Peterson said. “It was like 10 shots right away.”

The police weren’t looking in the direction of the gunman when he began shooting, she said.

Asked if the shooting was a planned ambush of police, Zibolski told reporters: “The investigation into that is still ongoing.” He said he believed police had previously had some sort of contact with Barakat “but not anything significant.” He did not know what type of gun Barakat used.

He said the state Bureau of Criminal Investigation and the FBI were investigating.

Zibolski said officer Jake Wallin, a military veteran, was killed, and officers Andrew Dotas and Tyler Hawes were wounded. Officer Zach Robinson shot and killed the suspect, Zibolski said.

Peterson, who said she has a bachelor’s degree in nursing, said her first instinct was to get out of her car and help. But her 22-year-old daughter, who was in the passenger seat, yelled that they had to take cover, so she drove around to the back of the bank.

At the time of the shooting, Wallin, 23, of St. Michael, Minnesota, was in the field as an officer in training, having become a Fargo police officer less than three months earlier. Wallin previously served in the Minnesota Army National Guard and was deployed to Afghanistan, Zibolski said.

“He served his country, came back here and wanted nothing more but to serve in a position with purpose and meaning – his exact words — and he did that,” Zibolski said.

In video played at a Saturday news conference showing Wallin training with fellow recruits, he spoke of his desire to pursue a career in law enforcement.

“Throughout my entire life, I’ve always wanted to work in some sort of position that had purpose behind my job and police officer is always what kind of came to me,” Wallin said. “I don’t want to be sitting in an office wondering why I’m here every day. I want to be out, I want to be doing something that I can tell myself at the end of the day I made a difference somehow.”

For nine hours after the shooting, police had called it only a “critical incident.” Early details emerged from people who said they witnessed the shooting or heard gunshots. Shortly after the shooting, officers converged on a residential area about 2 miles (3.2 kilometers) away and evacuated residents of an apartment building while gathering what they said was related evidence.

On Saturday, investigators were still at the apartment building, going back and forth from the third floor, where police tape hung across a hallway. Few residents were around and an FBI truck was out front.

Associated Press writers Margery A. Beck in Omaha, Nebraska, Ed Komenda in Seattle, Wash., contributed to this report.