The shooting erupted in the area of North Codorus Township, about 185 km west of Philadelphia.
Three police officers have been killed and two injured in a shooting in the southern part of Pennsylvania, US police say.
The shooting erupted in the area of North Codorus Township, about 185km west of Philadelphia, not far from the Maryland line, authorities said.
“The grief will be unbearable but we will bear it,” Pennsylvania State Police Commissioner Christopher Paris said at a news conference.
READ MORE: 'Priceless and eternal': Trump, Charles speak at lavish banquet
“We will not rest until we conduct a full, fair and competent investigation into this matter.”
York Hospital said it was treating two people in serious condition and had enhanced security protocols are in place.
“We grieve for the loss of life of three precious souls who served this county, served this commonwealth, served this country,” Governor Josh Shapiro said.
"This kind of violence is not OK, we need to do better as a society.”
Attorney General Pamela Bondi called the violence against police “a scourge on our society".
She said federal agents were on the scene to support local officers.
“Please send prayers to the officers and those involved in the shooting in York County,” Pennsylvania Lieutenant Governor Austin Davis said in a social media post.
Pennsylvania Attorney General Dave Sunday said he was also on the scene. Sunday said on social media he urges “all residents to follow the instructions of local law enforcement” and he is “praying for all involved”.
A local school district issued a shelter-in-place order, though it said schools and students were not involved in the shooting.
The order was lifted later in the afternoon.
The district said in a statement that authorities “advised us to hold students and staff in our buildings as a precaution while several area roads are closed”.
READ MORE: 'Pay attention': Passenger flight repeatedly warned to steer clear of Air Force One
The medical response unfolded on a rural road in south-central Pennsylvania that winds through an agricultural area with a barn and farm fields.
Police have not provided any details about who was involved in the shooting.
Officers were keeping people well back from the scene in the area’s rolling farmland, with some 30 police vehicles blocking off roads bordered by a barn, a goat farm and soybean and corn fields.
“Pennsylvania State Police, Northern Regional Police and numerous emergency responders are at the scene. The York County Commissioners are monitoring the situation closely and praying for all those involved," the county said in a statement.
An officer in the area was killed in February, when a man armed with a pistol and zip ties entered a hospital’s intensive care unit and took staff members hostage before a shootout that left both the suspect and an officer dead.
DOWNLOAD THE 9NEWS APP: Stay across all the latest in breaking news, sport, politics and the weather via our news app and get notifications sent straight to your smartphone. Available on the Apple App Store and Google Play.
More Aussies putting retirement on hold, working into their 70s than ever before
Trump says ideology that opposes fascism will be listed as terror group
Fears for pilot after light plane disappears after taking off from Sydney airport
Two face court for murder after 'amazing person' shot dead in Melbourne
Brittany Higgins lodges appeal over costly defamation loss to former boss
Sad scene off Queensland coast reignites shark net debate
Trump's historic feud with Kimmel spans almost 10 years and two presidencies
Coroner finds missing radio host was killed by croc
'Sad it's come to this': Why ice-cream icons split after nearly 50 years
Trump names his next target after Jimmy Kimmel pulled off air
The moment of Donald Trump's UK visit cameras weren't allowed to see
The Epstein files question the FBI Director refused to answer nine times
Who landed the best seats at Trump's UK state banquet
'Priceless and eternal': Trump, Charles speak at lavish banquet
