GRANTSVILLE, Utah – The teen accused of killing his mother and three siblings at their Grantsville home has been formally charged with four counts of 1^st degree felony aggravated murder.

With those charges, officials have released more details about Friday’s tragic shooting.

Prosecutors identified the suspect as 16-year-old Colin Jeffery “CJ” Haynie. Killed were 52-year-old Consuelo Alejandra Haynie, 15-year-old Alexis, 14-year-old Matthew, and 12-year-old Milan.

In a Wednesday afternoon press conference, Tooele County Attorney Scott Broadhead said their information indicated CJ Haynie stayed home from school on Friday.

#Breaking: Charges have been filed against 16yo Colin Jeffrey Haynie for shooting and killing his mother and 3 younger siblings. Charging documents indicate he murdered his siblings over the course of several hours as they returned home from school and work. #Grantsville @KSL5TV pic.twitter.com/paId6iozzL

— Garna Mejia KSL (@GarnaMejiaKSL) January 22, 2020

According to charging documents, Consuelo Haynie had gone to the school to pick up her daughter, Milan. Shortly after they returned home, officials said Colin shot and killed both of them with a handgun.

“The defendant murdered his mother and Milan not long after they returned home, by firing multiple rounds from a handgun into their heads, necks, and upper bodies,” Broadhead said.

Officials said when Alexis arrived home and was killed sometime between the first shootings and 5:17 p.m., when witnesses said Matthew arrived home.

Matthew died of a single gunshot wound to the head. Alexis also suffered multiple from gunshots.

The killings happened over the course of several hours.

“This wasn’t a one horrific act all occurring in one minute, ‘I snapped,’” said Broadhead. “This is something that methodically happened over a five-hour period.”

Authorities suspect the father, 50-year-old Colin, was the last to come home about an hour after Matthew, according to information he provided to officers.

“He said when he arrived at the family home at around 6:15 p.m., the defendant shot him in the leg. A struggle ensued and the defendant’s father was hit in the head with an unknown object, causing a laceration,” charging documents indicated.

Colin Haynie told detectives he was able to get the gun away from CJ.

The suspect reportedly told his father that his mother and siblings were dead, “and that his intention was to kill everyone in the house except himself.”

A neighbor who by coincidence was dropping off some keys then stopped by the home. Broadhead said the father answered the door and asked for help getting both he and CJ to the hospital.

On the way, the neighbor called 911 emergency dispatchers and told them that just before calling, CJ told her he had just killed his family.

Then during the call with dispatch, the suspect said he killed his mother first at about 1 p.m., and his other siblings as they returned home.

Officers then responded to the home and found the bodies of the victims inside.

Authorities said CJ has not been cooperating with police, and they haven’t spoken with his dad, Colin, since the incident.

Due to the nature of the crime, CJ will be tried as an adult by state law. However, because he is a minor, he is not eligible for capital punishment.

CJ Haynie has been charged with four counts of aggravated murder, one count of attempted murder, and five counts of felony discharge of firearm.

The charges carry a maximum sentence of life in prison without parole. His first court appearance will be on Monday at 1:20 p.m. in Tooele County.

In the meantime, funeral services have been planned for Friday at noon at the Grantsville Stake Center at 550 East Durfree Street. A viewing will be held prior to the funeral at 10 a.m., and interment will follow at the Grantsville City Cemetery on Main Street.

Broadhead said there was no previous history of violence at the family home. He confirmed the handgun used in the incident belonged to the family, although specifics were not immediately available.

Several items were confiscated from the family home, including computers. Detectives hoped to find evidence that will give them a better idea of the suspect’s motive and mental state.