A 15-year-old boy accused of killing his parents and three siblings at their home in Washington state shot them and then called police to claim that one of the victims killed his family and then himself, according to court documents.

The boy, whom NBC News is not naming because of his age, was charged Thursday with five counts of murder and one count of attempted murder in the slayings Monday morning in Fall City.

Two adults and three children — 7, 9 and 13 years old — were found dead…