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 signal peace deal near despite differences over terms
Trump says Iran war deal close as Strait of Hormuz tensions linger
Victims' families mark Air India crash anniversary with prayers and tributes
Ebola outbreak spreads to crowded displacement camp in Congo
Fire breaks out at New Zealand's Wellington airport, disrupting flights
