A shooter killed one person Friday in the lobby of New Hampshire's psychiatric hospital and then was fatally shot by a state trooper, officials said.

CPR was performed on the victim, who was transported to Concord Hospital before dying, officials said.

At a press conference, police said the shooting was contained to the front lobby and that patients were safe as of late Friday.

The state trooper who shot the gunman was not wounded in the attack. The motive of the shooter remains unclear.

New Hampshire Hospital, which has roughly 185 beds, is the only state-run psychiatric hospital for adults. It is located in the capital city of Concord, near Concord High School, multiple state agencies, and a district courthouse. It's located on a large campus comprising more than a 100 acres of land.

Democratic US Rep. Annie Kuster called the shooting “horrifying” in a statement and asked the public to stay away from the hospital while police worked the scene.

“Thank you to the State Police Officers who responded to the scene so quickly,” Kuster said in a statement. “My thoughts are with the victim, their family, and the Concord community."

Other members of the state's congressional delegation also released statements of support.

“The state immediately mobilised, and first responders and law enforcement are on the scene,” Gov. Chris Sununu said in a statement. “We will provide as many details as possible as this situation unfolds.”

Friday's shooting was the latest act of violence at a US hospital. Medical centres nationwide have struggled to adapt to the growing threats, which have helped make health care one of the nation's most violent fields.