Washington teen accused of annihilating his family checked their pulses to make sure they were dead, sole survivor claims

The 15-year-old boy from Washington state who allegedly killed his parents and three siblings chillingly checked their pulses to make sure they were dead after he shot them, the sole surviving family member told police.

The teen is charged with murdering parents Mark and Sarah Humiston, brothers Benjamin, 13, Joshua, 9 and sister Katheryn, 7, after opening fire with his father’s handgun at their $2 million suburban Seattle mansion last week.

As they lay covered in blood on the floor in the aftermath, he methodically walked over to three of the family members’ he’d killed in the hallway “touching their necks or chest to see if they were alive,” the boy’s 11-year-old sister told police.

She survived by playing dead and then escaping out a window.

The girl recalled through sobs being awoken by gunfire just before 5 a.m. and peeking out her bedroom door to see her father and her 13-year-old brother lying dead in a pool of blood in the hallway, according to charging documents obtained by The Post. 

Kathryn — with whom she shared a room and bunkbed — was then shot dead as she walked out of their bedroom and into the hallway to check on the noise. 

Her brother then came into the room and allegedly shot the 11-year-old in the neck and hand, left the room and checked the bodies in the hallway. 

He entered her room for a moment but she closed her eyes and held her breath pretending to be dead.

She escaped through a “fire window” in her room, fleeing into the street and running to a neighbor’s house, according to charging documents. Her neighbors called 911 and the girl was taken to Harborview Medical Center where she identified her 15-year-old brother as the shooter to authorities.

At the same time his neighbors were calling, the gunman also called 911 and told dispatchers that his 13-year-old brother had killed their family and “taken himself out.” He claimed that his brother had gotten in trouble looking at pornography the night before, sparking the rampage.

He then staged the bloody scene before first responders arrived in an attempt to pin the killings on his dead  brother, even putting a gun in his hand, according to the charging documents.

He was immediately taken into custody.

When asked about a possible motive, gunman’s sister told investigators he had recently gotten into “a lot of trouble” for failing some tests at school.

The 15-year-old was the only child in the family who knew the combination of the lockbox containing the Glock handgun, which her father kept by the front door to bring to work, she said.

Prosecutors charged the alleged teenage gunman — who was not identified due to his age — last Thursday with five counts of first-degree aggravated murder and one count of first-degree attempted murder.