ALFRED — Biddeford landlord James Pak pleaded guilty Wednesday in York County Superior Court to murdering two teenage tenants in 2012 after a dispute over parking spaces.

The mother of one, who also was shot but survived the attack, said she is routinely haunted by the experience and doubts she will ever get over it.

Pak, 77, shot and killed Derrick Thompson, 19, and his girlfriend, Alivia Welch, 18, in the apartment they and Thompson’s mother, Susan Johnson, rented from Pak at 17 Sokokis Road.

Pak also pleaded guilty to trying to murder Johnson, now 47. Johnson lay under their Christmas tree, pretending to be dead as Pak used a .357 Magnum to kill the two teenagers on Dec. 29, 2012.

In court, Pak wore an orange jail jumpsuit and used headphones to help with his hearing. About 35 friends and family members of the victims, many of them young people like Thompson and Welch, were in the gallery.

Justice John O’Neil made sure Pak understood the proceedings, given concerns about his cognitive ability and difficulty with English.

Pak said through his attorney, Joel Vincent, that he decided to plead guilty to spare himself, his wife and the relatives of the victims the ordeal of going through a trial.

Vincent explained that Pak originally had pleaded not guilty by reason of mental disease or defect, but subsequent psychological evaluations showed he was aware of the wrongfulness of his actions. Vincent told O’Neil that he and Pak explored whether he acted in self-defense, but the evidence showed that was not the case.

O’Neil asked Pak whether he disagreed with Vincent’s assessment.

“I am guilty and I’m not disagreeing,” he said.

Assistant Attorney General Leane Zainea then outlined the evidence against Pak that the state would have presented, had the case gone to trial.

Zainea described how Pak was angry and was evicting the victims because Welch had moved in with Johnson and Thompson. The day of the shooting, there had been a verbal altercation between Pak and Thompson about parking and where Thompson was shoveling snow. At one point, Pak used his fingers to form a gun as if he were shooting at Thompson.

Johnson called Biddeford police, who went to the apartment but left after they spoke to both parties and determined it was a civil matter, Zainea said.

Minutes later, Pak entered Johnson’s apartment and declared: “I am going to shoot you. I am going to shoot you all.” He shot Johnson first, then fired on Thompson and finally shot Welch in the back as she begged him not to shoot. Some people in the gallery sobbed as Zainea recounted the methodical slayings.

Zainea then told how Pak said he was not going to shoot Johnson’s 6-year-old son, who also was at home, because he had done nothing wrong.

Police later arrested Pak after a standoff and seized two guns from his house, one of them the .357 used in the shootings. Pak told authorities that he had shot the three and was not remorseful.

On Wednesday, Johnson spoke outside the courthouse and said that she is relieved that Pak pleaded guilty, but wishes it had happened three years ago.

She said that, every day, she remembers that terrifying ordeal and what was lost that night.

Johnson described her son and Welch as fun, respectful young people who avoided trouble.

“They were good kids. They were starting their life,” she said. “It’s not fair.”

Welch’s parents, Danny and Jocelyne Welch, also attended Wednesday’s hearing. They did not address the media afterward, but one of their attorneys in their civil case against the Paks, Stephen Schwartz, said the plea hearing was an emotional experience for them.

“I think my clients are relieved that Mr. Pak pled guilty and that there is a sense of justice,” he said. “However, this is one of the most unimaginable things that can happen, to lose a child and in this manner.”

Welch’s parents have filed a wrongful death and negligence lawsuit against Pak and his wife, Armit Pak. Johnson, who is represented by Daniel Lilley, also is suing the Paks.

Pak was allowed to meet with his wife before Wednesday’s hearing.

Pak’s sentence will be decided at a hearing Feb. 11. He faces 25 years to life in prison on each count of murder, and four to 30 years for the attempted murder.