Upset that his wife was going to leave him and take their young son, Steven R. Johnson sought refuge in the basement of their St. Paul home the evening of Jan. 6. He threw back a few vodka shots and then went to a box where he kept a loaded handgun he had stolen from his wife’s father over Christmas.

“Why did you take the gun out of the box?” asked Johnson’s attorney, Connie Iversen, during a plea hearing Friday.

“To scare her,” said Johnson.

But Johnson testified at the hearing that between 6 and 7 p.m. he stashed the gun in his back pocket, climbed the stairs to the second floor and shot his wife, Manya Johnson, once in the temple. He testified that he called her mother just minutes later, about 7:13 p.m., to keep up a daily phone routine to thwart suspicion. By 7:25 p.m. he was at a hardware store on University Avenue, buying the saw he would use to dismember his wife in the bathtub.

Johnson, 35, pleaded guilty Friday in Ramsey County District Court to premeditated first-degree murder and was immediately sentenced to life in prison.

“There is nothing I can say to make this better,” Johnson said. “Saying sorry is not enough; it will never be enough. I will live with this regret for the rest of my life.”

Judge Lezlie Ott Marek had little sympathy.

“Mr. Johnson, your crime was heinous,” she said. “It has shocked this community. By all accounts, Manya Jewel was a very fine human being, and she was a bright light to all those who knew her.”

Under questioning by Iversen, Johnson gave this account of the day he killed his wife:

The couple argued earlier that day because Manya Johnson, 32, found a bottle of liquor in the car and did not like her husband drinking. Their 3½-year marriage had been faltering since the birth of their son, who was 18 months old when his mother died.

Johnson testified that he had lunch with his family to celebrate his sister’s birthday while Manya Johnson stayed home with their son, Oliver. The plan was to open presents at the Johnson home in the 1400 block of Sheldon Av., but when his family arrived, Manya Johnson said the couple had dinner plans, which was false. His family left around 5:30 p.m.

The couple argued, and Manya Johnson told her husband he wouldn’t get custody of their son, he testified. That’s when Johnson went to retrieve the gun.

“Were you able to persuade her not to leave with Oliver?” Iversen asked.

“No,” he said.

“What did you decide to do?”

“I decided to stop her from leaving,” he said. Johnson testified that he stood in the bathroom doorway and shot his wife as she walked past him.

“My son was crying in the bedroom,” Johnson said. “He had heard the shot.”

Johnson admitted that he began a series of cover-ups: He called his mother-in-law, dismembered his wife, cleaned up afterward and drove his wife’s car to a park-and-ride lot so it would look like she had gone to work Monday morning at Target Corp., where she worked in marketing operations.

He smashed her cellphone and left it under her car to fake an abduction, he said, then rode a bike home.

At 8:01 a.m. Monday, he sent his wife an e-mail, as was their practice. He took his son to day care and went to work.

Manya Johnson’s friend and co-worker texted Johnson about 11:29 a.m. concerned about her whereabouts.

“I played along like I didn’t know where Manya was,” he testified.

Johnson said he e-mailed his wife at 11:30 a.m. “to play the charade.”

That afternoon he drove plastic tote bags containing his wife’s body to a friend’s home in White Bear Lake and stashed them in a garage without the friend’s knowledge.

At 12:37 p.m. he called 911. At 12:42 p.m. he called St. Paul police to report his wife missing. At 1:30 p.m. he met with his friend, whom he had befriended in prison, and confessed to his crime. But an hour later Johnson met up with his wife’s co-worker and searched for her, he testified.

Police intercepted him at the family’s home that afternoon.

Johnson said Friday that his wife “had a huge heart,” and that she had accepted him despite his criminal past.

“I did not deserve her,” he said. “I robbed my son of his mom and his dad. I have robbed her family of their daughter and their sister and their friend.”

As part of the plea agreement, a second-degree murder charge was dismissed and the state agreed not to oppose any attempts Johnson could make for early release after serving 30 years in prison.

Steven and Manya Johnson’s families declined to comment after the hearing. Manya’s parents are caring for the boy.

In court documents from Johnson’s 1996 conviction for aiding and abetting criminal sexual conduct in Anoka County, a psychologist diagnosed the 18-year-old as “particularly defective in his capacity for empathy” and as having “a pathological sexual adjustment that is not likely to be improved very much by the time he leaves prison.”

Johnson was sentenced to 17 years and two months in that case. He met Manya Johnson soon after his release from prison in February 2008.