Three law enforcement officers were killed and two others were critically wounded in a shooting in Pennsylvania on Wednesday afternoon, the state police commissioner said.

Police were apparently serving a warrant in York County when they were fired upon, three sources familiar with the matter told NBC News.

The officers were in Codorus Township following up on a domestic investigation that began Tuesday, said the state police commissioner, Col. Christopher Paris.

“There are simply no words I can offer to assuage the grief that this community has experienced,” he said.

The two surviving officers were in critical but stable condition at WellSpan York Hospital, he said.

Paris said police fatally shot the suspect, who was not immediately identified.

The first 911 call came in from North Codorus Township at 2:10 p.m., said Ted Czech of the York County Office of Emergency Management.

Dave Miller told NBC affiliate WGAL of Lancaster that he was driving home and had pulled over to clear the way for police and heard the gunfire.

“I looked over to the right, of course, and I saw the police in the barn, looked like they were looking for someone,” he told the station. “And then I heard the gunshots ring, and I saw people on the ground.”

Miller said the person on the ground appeared to be a police officer. He said he heard around 30 shots.

“It was just continuous,” he said. “Lots of shots, more than what I could count.”

Pennsylvania Gov. Josh Shapiro asked for prayers for the officers’ families. He called it "a tragic and devastating day" for York County and the state.

Shapiro said that he spent time with the families and that even though they were grieving, they took time to say "how proud they are of their loved ones who put on a uniform to keep us safe."

"This kind of violence isn't OK," Shapiro said. "We need to do better as a society. We need to help the people who think that picking up a gun, picking up a weapon, is the answer to resolving disputes.

The officers were not immediately identified. Paris did not name their department, citing the investigation.

Paris did not release details about how the shooting occurred. He called the crime scene large and active but said there is no further threat to the community.

Attorney General Pam Bondi said in a statement that the FBI and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives were assisting, and she said, "Violence against law enforcement is a scourge on our society and never acceptable."

Bondi reached out to Shapiro and said the state has the full support of the federal government, Shapiro said.

Shapiro ordered flags lowered to half-staff Wednesday in honor of the slain officers.

The deadly shooting comes almost seven months after another police officer in York County, West York Patrolman Andrew W. Duarte, was killed as he was responding to a hospital siege in which a gunman took hostages.