Dubuque, Iowa ? A high school tennis coach and Cub Scout leader faces life in prison after pleading guilty to first-degree murder for killing his two children.

Michael Walker also pleaded guilty Thursday to attempted murder of his estranged wife, Karen, as well as to killing his daughter Lindsay, 9, and son Jordan, 8, on Feb. 17. He will be sentenced June 2. First-degree murder carries a mandatory life sentence.

“I put Lindsay in my lap and held my hand over her mouth and held her nose closed till she wasn’t breathing anymore,” he said during last week’s hearing. “Then I put Jordan on my lap and held my hands around his throat till he wasn’t breathing anymore.”

Walker said he went to Karen’s apartment, two blocks from his apartment.

“I proceeded to stab her and cut her throat so she would die and join her children,” he said.

Karen survived, but she was hospitalized for more than a week with life-threatening stab wounds.

Walker, 38, said he had planned to commit suicide afterward so the family could be together.

Dubuque County Atty. Fred McCaw said Walker decided about a week ago to change his initial innocent plea. His trial had been scheduled for April 28.

About 20 people, mostly investigators, filled a Dubuque County Courtroom for Walker’s first court appearance since his arrest.

His attorneys, public defenders Tom Goodman and Paul Kaufman, sat on either side of their client, while McCaw and Assistant Dubuque County Atty. Chris Corken represented the state.

Dubuque County District Court Judge Alan Pearson asked Walker several questions to make sure he understood what was taking place. Walker said he was on medication for bipolar disorder but could understand the proceedings.

Walker’s brother, Christopher White Walker, editor and publisher of The Emporia (Kan.) Gazette, has said his brother has battled bipolar disorder, or manic depression, all of his life.

The plea was against the advice of his attorneys, Goodman said.

“It’s not the recommendation of our office that Mr. Walker go forward today, but this is the way he wanted to do this,” Goodman told the judge.

The defense had Walker examined by two physicians who concluded that Walker could not use any special defenses under the state’s legal standards, Goodman said. However, he said there was “no question” his client had a mental illness.

Walker tearfully told the judge it was because of Jordan, Lindsay and Karen that he was pleading guilty.

“Those are the three reasons that this plea is the only plea I can do,” he said. “No matter what state of mind I was in or where I thought we would go as a group afterward, a trial would only bring this up again, and I can control that, and I wish to.”

Walker clutched photos of his children and continued to cry as he told the judge he had been planning the events since 2 a.m. or 3 a.m. the day before the slayings. He was going to send an e-mail to relatives after he killed his family. Then he was going to take his own life, Walker said.

“I wanted to be with my family, and since I couldn’t be with them in life I was going to be with them in death,” he told the court.

Michael and Karen Walker were married in 1991 but had been separated since at least last summer, police said. The children spent most of their time at their mother’s home, although they were staying with their father the night they were killed.

Walker was married once before and has two other children, Matt, 15, and Kristen, 13.

He was involved in the community as a Cub Scout leader, an active member of the Dubuque chapter of the United Way and as varsity girls tennis coach at Dubuque Senior High School.