The gunman in Friday’s shooting at Marysville-Pilchuck High School had invited his friends to join him for lunch, said Snohomish County Sheriff Ty Trenary.
During a news conference Monday, Trenary said the gunman, whom witnesses have since identified as Jaylen Fryberg, had sent text messages to five people to arrange a gathering in the cafeteria.
"Witnesses confirm that the five victims were at the table when the shooter opened fire, striking the victims before turning the gun on himself," Trenary said.
The sheriff also said the .40-caliber handgun used during the shooting was registered to a family member of the gunman and had been legally purchased. Detectives have not yet determined how the shooter gained possession of the weapon, Trenary said.
Investigators don't have a motive for the shooting that claimed three lives, including the gunman's, and left three others injured.
"Candidly, I don't know that the 'why?' is something that we can provide," Trenary said. "I think our focus has to be on Marysville-Pilchuck, on the Tulalip Tribes and the communities. And we know from these [incidents] that have occurred all across the country that sometimes the why is elusive, but I think it’s more important for us to focus on the pain and anguish that those families are experiencing."
Two students were fatally wounded during the shooting. Zoe R. Galasso, 14, died of a gunshot wound to the head Friday. A second victim, 14-year-old Gia Soriano, was taken to Providence Regional Medical Center with a head wound. She died Sunday.
Three other students were injured. Two remain in critical condition while the third victim was upgraded to satisfactory condition Monday.
The full investigation is expected to take several months, Trenary said.