A police officer was shot and killed Sunday outside a Maryland police station in an "unprovoked attack", authorities said

A second person, not a police officer, also was shot and wounded, police said. Two suspects in the officer's shooting were in custody.

Police identified the slain officer as 28-year-old Jacai Colson, a four-year veteran of the Prince George's County Police Department who was days shy of his birthday.

"One of your defenders lost his life in defense of this community today," Police Chief Hank Stawinski said Sunday night.

The shooting occurred Sunday afteoon outside the Landover police station in Prince George's County, a suburb of Washington, D.C.

Law enforcement sources told FOX 5 DC that the attack was "ambush-style."

Maryland Gov. Larry Hogan said in a statement Sunday night he was "shocked and saddened" over the officer's killing.

"It is my hope that his proud legacy of commitment and passion for law enforcement and serving others will provide some comfort in the difficult days that lie ahead," he said.

Police had initially posted a message on Twitter asking residents to avoid the area and to stay inside because of a possible "active shooter" situation.

Alan Doubleday, assistant chief of the Prince George's County Fire and Emergency Services Department, told the Associated Press that a person who was shot was taken by ambulance to Prince George's Hospital Center. That person, who was not a police officer, appeared to be in stable condition, Doubleday said.

The Washington Post reported that one woman near the site grabbed her sleeping, 14-month old baby from his play pen when she heard what she thought might be either firecrackers or gunshots. The woman told the newspaper she looked outside and saw a man dressed in black firing a handgun.

"He fired one shot, and then he started pacing back and forth, then fired another shot," said Lascelles Grant, a nurse. She added in the account that police began pouring out of the station. "Just looking outside, I'm like, 'Oh my God, look at all these police officers ruing out, putting their lives really in danger.'"

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives have begun assisting local police in the investigation, spokesmen for the two federal agencies said. They said the Prince George's County Police remained the lead investigating agency.

Dave Fitz, spokesman for the FBI in Maryland, told the AP that the FBI "reached out and offered support" and sent a couple of special agents to assist. He had no further details.

Dave Cheplak, spokesman for the ATF in Maryland, was unable to say how many ATF agents were assisting. He also could not say specifically what they are doing, but said assistance typically would include following up on leads, interviewing witnesses, supporting evidence collection and tracing any recovered firearms.

The Prince George's County Police Department's District III station is next door to county police headquarters. Nearby is the Palmer Park Community Center, although a county website listing for the center says it is closed on Sundays.

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The Associated Press contributed to this report.