Four law enforcement officers have been fatally shot and four others were wounded while serving an arrest warrant in Charlotte, North Carolina.
A suspected attacker was found dead in the front yard of a barricaded home after a standoff that lasted three hours, police said.
Two other persons of interest were taken into questioning, authorities added.
It is one of the deadliest assaults on US law enforcement in recent years.
The officers were part of a US Marshals Service-led task force. The warrant they were attempting to serve on Monday was against a felon wanted for illegally possessing a firearm.
Gunfire erupted on the suburban street as they tried to do so.
The officers returned fire at an assailant in the front yard, then more shots were fired at them from inside the home, Charlotte-Mecklenburg Police Chief Johnny Jennings told a news conference. A high-powered rifle was found inside the property, he added.
“Today we lost some heroes who were out simply trying to keep our community safe,” the police chief told reporters.
He said it was the worst attack on police officers he could recall in his 30 years on the force.
Shots were still ringing out more than two hours after the attack began in a residential area in the east of the city, according to witnesses.
The assault ended when police stormed the home on Galway Drive in the Shannon Park neighbourhood, using armoured vehicles to smash their way in, destroying windows and doorways.
Two women who were inside the home with a suspect were taken in for questioning, police said. Police believe there was more than one attacker involved in the incident.
The US Marshals Service confirmed in a statement that one of its officers had been killed in the raid.
North Carolina Governor Roy Cooper said two of the officers killed were members of the state’s Department of Adult Corrections (NCDAC).
They were identified as Sam Poloche, who joined NCDAC in 2013, and William “Alden” Elliott, who joined in 2016.
“Our hearts are with the families and co-workers of officers in today’s brutal attack,” he posted on X, formerly Twitter.