At least six people died and at least nine were injured in an early-morning shooting in Sacramento, California, the city's police department said on Twitter.
Police said several blocks of a commercial stretch of the downtown area were closed while they investigate. Videos posted online showed people shouting and running in the street.
Reuters could not independently verify the footage.
The incident comes a little more than a month after a man shot and killed his three children and a fourth person before taking his own life in the same city.
US and Iran exchange attacks as lull in war appears over
Malta court clears businessman over murder of investigative journalist
Kuwait confirms no injuries after Iranian drone hits residential complex
Nepal flood rescue hopes dim as China restores access to Tibet disaster zone
At least 21 die in bus accident in Egypt's South Sinai, ministry says
Defendant pleads not guilty in Charlie Kirk capital murder case
Nepal flood death toll crosses 1,000, rescuers reach remote areas
UK pledges additional £50 million to help contain Ebola outbreak in Congo
