(ABC News) -- A Ludington, Mich., man is facing a murder charge for allegedly killing his infant daughter who disappeared more than two years ago, prosecutors said.
Michigan Attorney General Bill Schuette and Mason County Prosecutor Paul Spaniola said they filed an open murder charge against 23-year-old Sean Phillips on Friday for the death of his daughter, Katherine Phillips, known as Baby Kate.
"The filing of this open murder charge moves us one step closer to securing justice for Baby Kate," Schuette said in a news conference.
Katherine Shelbie-Elizabeth Phillips went missing on June 29, 2011, when she was only four-and-a-half months old. Katherine's mother, Ariel Courtland, identified Sean Phillips as the alleged kidnapper.
The day Baby Kate vanished, Courtland and Phillips had run an errand near their home in Ludington, about 80 miles west of Grand Rapids, police said. They evidently got into an argument and Phillips allegedly took off with the child, according to police.
Phillips was arrested at his parents' home the next day, but police found no trace of Baby Kate.
She was last seen wearing a white one-piece outfit with black polka dots, and black and pink flowers. At the time of her disappearance, she had no hair, blue eyes and was teething.
"This was first to believed to be a 'missing person's' case. And law enforcement conducted an extensive search for Baby Kate," Schuette said in a news conference Friday. "Now, unfortunately, we will never be able to bring Baby Kate back. She was an innocent victim of a terrible crime at the hands of her own father, no less. This is a tragic case. It just makes you sick. There will be no first birthday party for Baby Kate. No first day of Kindergarten. No first Christmas."
Phillips was arraigned from prison during a videoconference on Friday, and will receive a court-appointed attorney. He was in custody at Carson City Correctional Facility in Carson City, Mich., where he was already serving a 10-year minimum prison sentence, according to the Michigan Department of Corrections website.
He was convicted in August 2012 of unlawful imprisonment in his daughter's disappearance.
An open murder charge means a jury can consider both first- and second-degree murder convictions. The maximum penalty for the conviction in the state is life in prison.
Courtland and her family attended the news conference, as well as the arraignment.
She told The Associated Press it was a "slap in the face" for her to not learn about the charges before the news of the charges broke. She believes there's a chance Kate still may be alive.
"We don't know and we need to keep the hope that she's going to come home," Courtland said.