A teenager in Utah accused of fatally shooting four of his relatives and wounding a fifth will be charged as an adult as soon as Wednesday, a prosecutor said.

Tooele County Attorney Scott Broadhead told KUTV-TV that prosecutors still don't know what the 16-year-old boy's motive was in shooting the three children and their parents Friday night in the small town of Grantsville west of Salt Lake City.

"He has not talked to the police or anyone in authority, so we don’t really know what he was thinking, what his thoughts were, what his motivations were," Broadhead said.

Photographs of Consuelo Alejandra Haynie, 52, right, and three of her children, 12-year-old Maylan, 14-year-old Mathew, and 15-year-old Alexis Haynie, left to right, are displayed at a candlelight vigil for the Haynie family at City Park in Grantsville, Utah, Monday, Jan. 20, 2020. Police say four members of the Haynie family were killed and one injured after being shot by a teenage family member on Jan. 17. (Spenser HeapsThe Deseret News via AP)

Photographs of Consuelo Alejandra Haynie, 52, right, and three of her children, 12-year-old Maylan, 14-year-old Mathew, and 15-year-old Alexis Haynie, left to right, are displayed at a candlelight vigil for the Haynie family at City Park in Grantsville, Utah, Monday, Jan. 20, 2020. Police say four members of the Haynie family were killed and one injured after being shot by a teenage family member on Jan. 17. (Spenser HeapsThe Deseret News via AP)

Prosecutors planned to meet with Grantsville police on Wednesday, and charges would be filed sometime after that. He is expected to be charged in district court, which has jurisdiction in cases of anyone over the age of 16 charged with aggravated murder or murder.

Authorities have declined to name him or specify his relationship to the victims before charges are filed.

Grantsville police officials have said the teenager is facing as many as 10 charges, including aggravated murder.

People gather for a candlelight vigil for the Haynie family at City Park in Grantsville, Utah, Monday, Jan. 20, 2020. Police say four members of the Haynie family were killed and one injured after being shot by a teenage family member on Jan. 17. (Spenser HeapsThe Deseret News via AP)

People gather for a candlelight vigil for the Haynie family at City Park in Grantsville, Utah, Monday, Jan. 20, 2020. Police say four members of the Haynie family were killed and one injured after being shot by a teenage family member on Jan. 17. (Spenser HeapsThe Deseret News via AP)

Prosecutors would not be allowed to seek the death penalty because the boy is a minor. The possible prison sentence for an aggravated murder conviction is 25 years to life.

The funeral for Consuelo Alejandra Haynie, 52, her 15- and 12-year-old daughters and her 14-year-old son will be held Friday. The injured husband and father, 50-year-old Colin Haynie, has been released from the hospital and was talking with investigators.

The family moved to Grantsville in 2010 and they have two other children, according to an obituary for Alejandra Haynie and the children.

Police investigate after four people were killed and a fifth person was injured in a shooting at a Grantsville, Utah, home Friday, Jan. 17, 2020. The suspected shooter was taken into custody by Grantsville police, the Deseret News reported. Grantsville Mayor Brent Marshall said the victims and the shooter are all related, the newspaper reported. (Steve GriffinThe Deseret News via AP)

Police investigate after four people were killed and a fifth person was injured in a shooting at a Grantsville, Utah, home Friday, Jan. 17, 2020. The suspected shooter was taken into custody by Grantsville police, the Deseret News reported. Grantsville Mayor Brent Marshall said the victims and the shooter are all related, the newspaper reported. (Steve GriffinThe Deseret News via AP)

Jack and Holly Nelson, center, join others in prayer during a candlelight vigil for the Haynie family at City Park in Grantsville, Utah, Monday, Jan. 20, 2020. Police say four members of the Haynie family were killed and one injured after being shot by a teenage family member on Jan. 17. (Spenser HeapsThe Deseret News via AP)

Jack and Holly Nelson, center, join others in prayer during a candlelight vigil for the Haynie family at City Park in Grantsville, Utah, Monday, Jan. 20, 2020. Police say four members of the Haynie family were killed and one injured after being shot by a teenage family member on Jan. 17. (Spenser HeapsThe Deseret News via AP)