It had caused six deaths and twelve injuries.
Two brothers suspected in the shooting last weekend in Sacramento are in the hands of the police.
According to the investigators, the two young people were in particular in possession of prohibited firearms.
One of the brothers, Smiley Martin, was among 12 people hospitalized after being injured in the shooting, which occurred early Sunday morning in downtown Sacramento.
This is the brother of Dandre Martin, 26, arrested Monday for assault and illegal possession of a firearm.
Smiley Martin, 27, is under police surveillance in hospital where he is being treated for "serious" injuries, is suspected of having been in possession of a "submachine gun".
A third man, Daviyonne Dawson, found in possession of a firearm shortly after the shooting, was also arrested.
At this stage of the investigation, the police have not specified the circumstances in which this violence broke out, in particular whether the shooting was aimed at specific individuals or whether the perpetrators had opened fire at random.
The drama could have been triggered by a fight at the closing of a nightclub.
More than a hundred casings were found at the scene of the tragedy by the investigators.
More guns than people in the United States
The tragedy occurred around 2 a.m. Sunday in downtown Sacramento, the time when the many bars and nightclubs in this bustling neighborhood close their doors.
A video circulating on social media appears to show a fight in the street involving several people, followed by a series of detonations and individuals running.
Shootings in public places are common in the United States, whether in schools, shopping malls or supermarkets.
According to the Small Arms Survey program, in 2017 there were about 393 million guns in the United States, more than people.
