MARYSVILLE — A freshman who shot five young people in the Marysville Pilchuck High School cafeteria sent text messages to his victims, arranging for the group to sit with him at lunch, Snohomish County Sheriff Ty Trenary said Monday.

Since Friday afternoon detectives have been carefully piecing together what happened inside the cafeteria. They are scouring phone and text records between the shooter and his victims. The boy’s parents agreed to allow detectives to seize the shooter’s electronics and search his room. The sheriff expects that the investigation will take months.

Trenary said he hopes people will focus less on possible motives and more on helping the community recover.

“Candidly, I don’t know the ‘Why?’ is something that we can provide,” Trenary said at a press conference.

Jaylen R. Fryberg, 14, opened fire late Friday morning in a bustling cafeteria. The freshman athlete, a Tulalip Tribal member, then turned the .40-caliber Berretta on himself. Jaylen died from a self-inflicted gunshot wound to the head, the medical examiner confirmed Monday. His death was ruled a suicide.

Zoe R. Galasso, 14, was shot in the head and died at the scene. Her death was ruled a homicide.

Gia Soriano, 14, died Sunday night at Providence Regional Medical Center Everett, Dr. Joanne Roberts, the hospital’s chief medical officer, confirmed. The medical examiner is expected to determine the cause of her death later.

Shaylee Chuckulnaskit, 14, was still in critical condition at Providence.

Andrew Fryberg, 15, also remained in critical condition in intensive care at Harborview Medical Center in Seattle. Nate Hatch, 14, was upgraded to satisfactory condition. Harborview reported that he is awake and breathing on his own. The boys are cousins of the shooter.

Nate appeared to be posting on Twitter on Monday, including a message of love and forgiveness toward Jaylen Fryberg.

The three boys were close and the group had gone to homecoming together the week before.

Trenary said detectives are committed to a thorough investigation.

“Our responsibility is to work on behalf of the victims and in doing so we must collect facts,” Trenary said.

The shooting is being investigated by the Snohomish County Multiple Agency Response Team, a cadre of homicide detectives from around the county.

The sheriff said he wouldn’t speculate on anything being reported by media or on social media that had not been confirmed by detectives.

He believed the shooter had attended classes that day. The school district declined to verify that information on Monday, citing student privacy laws.

Witnesses confirmed that the five victims were at the table when the shooter opened fire.

The sheriff’s office also provided more detail about the actions of a first-year teacher who reportedly confronted the teen. Trenary said there was no physical contact between her and the shooter.

Detectives are still trying to determine how Jaylen obtained the handgun. It was legally purchased and registered to one of the shooter’s relatives, the sheriff said.

Trenary said he had no information about rumors that Jaylen left behind a letter for his family.

“We want to find answers to this tragedy as much as you do, but there is a process and right way of doing so,” he said.

Reporter Rikki King contributed to this story.

Diana Hefley: 425-339-3463, hefley@heraldnet.com. Twitter: @dianahefley