Part of a sign that reads "Cracked But Not Broken," hangs Monday, Oct. 27, 2014, at a growing memorial on a fence around Marysville Pilchuck High School in Marysville, Wash. On Friday, Oct. 24, a student opened fire in the school cafeteria, killing two fellow students before taking his own life. The school will be closed all week. (Ted S. Warren/AP)

DAYS BEFORE 15-year-old Jaylen Fryberg strode into his high school cafeteria and fired a gun at friends and finally himself, he wrote a tweet that hinted at some kind of problem: “It breaks me . . . it actually does. . . . I know it seems like I’m sweating it off. . . . But I’m not.” The words are now being plumbed by authorities for clues to help explain last week’s murderous rampage at Marysville-Pilchuck High School in Washington state.

Whatever the why behind this boy’s actions — it has been speculated that he either was bullied or was despondent over a girl — it should not detract from the horror of how three young people, including two 14-year-old girls, died and three more were injured. Nor should it obscure the sickening ease with which children can get their hands on guns.

The source of the gun in the shooting has been almost an afterthought in much of the reporting. But it appears, according to sources quoted in news reports, that the .40-caliber Beretta handgun was legally purchased, registered and owned by Jaylen’s father. That, according to Dan Gross, president of the Brady Campaign to Prevent Gun Violence, fits a deadly pattern: In two-thirds of the nation’s school shootings, the attackers used guns from their home or a relative’s residence.

More needs to be reported about how Jaylen obtained the weapon, but a recent report by the campaign’s sister organization makes clear that more attention must be paid to the threat of gun violence to young people. Shooting is a leading cause of death among children and teens; 60 percent of youth gun deaths occur in homes.

No doubt it is important to know what was behind the actions of this seemingly popular high school freshman and whether signs of trouble went undetected. But we can’t help but wonder whether the outcome would have been different if not for his ability to get a gun. After all, encountering problems and experiencing disappointments is not all that unusual for adolescents; it is part of growing up.

Sadly, though, growing up is something Jaylen Fryberg, Zoe Galasso and Gia Soriano will not experience.