Three white men were killed and another wounded when a black gunman opened fire in Fresno, California, in a suspected race attack, police have said.
Kori Ali Muhammad shot 16 rounds in 90 seconds in the shooting spree on Tuesday, said Police Chief Jerry Dyer.
He shouted "God is greatest" in Arabic when arrested but this was a hate crime not terrorism, Mr Dyer believed.
Mr Muhammad, 39, was also wanted for the murder of a security guard outside a motel in the city last week.
The mass shooting may have been sparked by the release of his photo to the media on Tuesday afternoon, police say.
Dozens of people marched to the downtown shooting scene on Tuesday afternoon to show support for "peace and reconciliation".
A Muslim leader in the city said Mr Muhammad did not represent Islam.
Why America remains segregated
All four victims were white men, and one of them was shot sitting in a car. Media in the city named him as Zackary Randalls, a 34-year-old father of two who was on his first day in his new job as a utility worker.
The suspect had indicated on social media that he hated white people and expressed anti-government views, police said.
"He wanted to kill as many people as he could and that's what he set out to do," said Mr Dyer.
"This was a random act of violence. These were unprovoked attacks by an individual who was intent on carrying out homicides today."
Mr Dyer added that Tuesday's attack "has nothing to do with terrorism in spite of the statements that he [Kori Ali Muhammad] made".
"He did clarify that the reason he had made that statement was that in the event that anything did happen to him that he was in fact pledging his allegiance to God for protection."