Carlos Morales, 18, of Sioux City, entered his written plea Monday in Woodbury County District Court to first-degree murder, going armed with intent and three counts of reckless use of a firearm. A trial date has yet to be set.
He is one of three charged with firing at least 27 shots into a house at 2636 Walker St., where 20-25 people were gathered for a New Year's party shortly after midnight on Jan. 1. Mia Kritis, 18, was struck and killed and three others were injured.
Morales' brother, Christopher Morales, 19, of Sioux City, pleaded not guilty last week to identical charges. He also faces gun charges stemming from his arrest. His trial has not been scheduled.
Anthony Bauer, 18, of Sioux City, faces the same charges as Carlos and Christopher Morales and has yet to enter his plea.
If found guilty of first-degree murder, the three would face a mandatory sentence of life in prison without parole.
Liliana Gutierrez, 20, of Sioux City, who is accused of driving the three to and from the house, was formally charged Monday with intimidation with a dangerous weapon and three counts of reckless use of a firearm. Her arraignment was set for Feb. 12.
All four remain in custody.
Christopher Morales was arrested in possession of a 9mm handgun that has been linked to the shooting. Police continue to search for a second handgun and an assault-style rifle also believed to have been used.