Police said the suspect in the shooting in Grantsville, Utah, is an event that police believe is a relative of the four people who died and the man who survived.
All the victims were from the same family, Corporal. Ronda Fields said at a news conference.
Officers found Consuelo Alejandra Hay, 52, dead with three of her children, Alexis, 15, Matthew, 14, and 12-year-old Mylan.
The children’s father, Colin Hay, was the only survivor. Fields said he was discharged from hospital on Monday.
Police have not released the suspect’s name because it happened, and Fields said they could not provide any details about his relationship with the victims.
Fields said the suspect, who has been charged with four counts of premeditated murder and attempted premeditated murder, refused to cooperate with investigators.
Fields said the young man “surrendered peacefully, although he refused to speak to the detectives.”
Police are still trying to set a timeline of events for the day of the shooting. Fields said the police responded to the call around 7 p.m.
The shooter and their father were gone when police arrived, and officials later discovered that someone had arrived after the shooting and took the two to hospital.
Officials say the town of 11,000 people has been shaken by the killings.
“Our hearts are with the families, loved ones, and the interconnected neighborhood that has been affected by this emotional and tragic accident,” said Grantsville Mayor Brent Marshall at the press conference. Counseling will be provided to fellow student victims when the school returns to Tooele County.
Fields said, “There are a lot of ends that must be restricted, and there are a lot of questions that we would like to answer. Unfortunately, there are some questions that we may never be able to answer,” adding: “The biggest question everyone has is: Why?