All four of the dead and the six treated for "non life-threatening" gunshot wounds were men aged between 25 and 35, Reed said.
"Our heart goes out to the families of the victims... this is senseless violence, he added. "We are doing everything we can to bring the perpetrators to justice."
Reed said it was unclear how many perpetrators had been involved in the shooting and that there was "no indication" the incident was gang-related.
Police spokesman Bill Dooley said officers were looking for surveillance footage and witnesses to track the suspects.
He said the victims were a group of family and friends who had gathered at the residence to watch a football match.
Fresno councillor Luis Chavez, who represents the district where the shooting took place, said the incident was "not a reflection of our community."
"Our officers are working diligently to piece together the sequence of events that led up to this, but more importantly to bring all those involved to justice," he said, in comments reported by the Fresno Bee newspaper.
Shootings are a frequent occurrence in the United States, but despite the scale of the gun violence problem in the country, efforts to address it legislatively have long been largely deadlocked at the federal level.
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