A police officer and three other people were killed when a domestic dispute at a bank escalated into shootings at three locations in Wisconsin.
The shootings happened at a bank, a law firm and an apartment complex, where officers, including a SWAT team, had a stand-off with the suspect for several hours which ended in a volley of gunfire around 5pm local time on Wednesday.
A suspect was in custody after the violence in a cluster of small towns south of Wausau, in northern Wisconsin about 90 miles west of Green Bay.
The authorities held a brief news conference late on Wednesday when they said there was no remaining threat to the public. They gave no details on the four victims of the suspect.
Jason Smith, a deputy administrator for the state Department of Justice's Division of Criminal Investigation, said more than 100 officers were investigating and more information would be released on Thursday.
The dead officer worked for Everest Metro, a small, 27-officer force that serves Schofield and Weston.
Everest Metro Chief Wally Sparks said: "I would like to send all my thoughts and ask everybody listening, 'Thoughts and prayers to all the victims and their families'. Please keep them in your prayers and be with our officers."
The first shooting was reported shortly after midday at Marathon Savings Bank in nearby Rothschild. Officers responding to a reported "domestic situation" at the bank arrived to find two people had been shot. They said the suspect was gone when they arrived.
A second call came about 10 minutes later from the Tlusty, Kennedy and Dirks law firm in nearby Schofield. The third shooting happened at 1.30pm at an apartment complex in Weston.
A woman who lives in the complex said she looked out of her window at the complex about 1.15pm to see a squad car approach, and a few seconds later heard a gunshot and saw the officer fall.
Kelly Hanson, 21, told The Associated Press she saw other officers put the wounded policeman in an armoured SWAT vehicle and take him away.
"I thought, what is going on? I know what a gun sounds like, and thought this isn't good," she said.
She said she stayed in her flat until about 4.45pm when she heard a volley of about 10 shots and began to "freak out".
The authorities eventually let her leave her flat.
"It's tragic that had to happen, but I think they did a good job out here today," Ms Hanson said.
SWAT members entered the apartment building about 2.30pm, the Wausau Daily Herald reported. Nearby schools and a hospital went on lockdown.
Omar Sey, 31, who said he had just moved to the building, learned of the shooting after he arrived home to find dozens of police cars outside.
Mr Sey, who had moved to Wisconsin from Gambia, said he did not understand why such things happen in America.
"This is crazy," he said. "You have everything at your disposal. Why don't you make your life better instead of engaging in this?"