TOOELE COUNTY (ABC4 News) – A Grantsville teenager is charged with the murder of his mother and three siblings, and the attempted murder of his father.

Tooele County Attorney Scott Broadhead announced formal charges against Colin Jeffrey “CJ” Haynie, 16, in the deaths of Alejandra Haynie, 52, Alexis Haynie, 15, Matthew Haynie, 14, and Milan Haynie, 12, and the attempted killing of Colin Haynie.

Prosecutors allege CJ Haynie shot and killed his family members in the span of about five hours on January 17.

“We have no answer at this point as to what his motive and his mental state was,” said Broadhead.

According to a probable cause statement, the Tooele County Dispatch Center received a call from a neighbor who said that CJ and Colin Haynie were in her car, and they were on their way to the hospital.

Watch: Tooele County Attorney Scott Broadhead announces charges

CJ reportedly told the neighbor that he killed his mother first around 1 p.m. and killed the others as they returned home.

Grantsville police responded to the Haynie home and found his mother and his three younger siblings dead.

Based on witness interviews, investigators outlined the timeline for the killings. Investigators said Alejandra picked up Milan from school that let out at 1 p.m.

Prosecutors said that the 16-year-old killed his mother and Milan as they returned home from school pickup.

Around 2 p.m. Alexis came home from school. Sometime between when she got home and 5:17 p.m., she was killed.

Around 5:17 p.m. is when Matthew got home and was killed.

Colin Haynie, CJ’s father, told police he arrived at the home around 6:15 p.m. and CJ shot him in the leg, but he was able to wrestle the gun away.

CJ Haynie is formally charged with four counts of aggravated murder, one count of attempted murder, and five counts of felony discharge of a firearm in Third District Court in Tooele County.