The “Twilight killer” teen who stabbed his girlfriend’s mom and sister to death gave a chilling of the incident to police after the murders, which aired on the UK show Murdered By My Daughter, on Thursday evening.

Lucas Markham was 14 in April 2016, when he snuck into girlfriend’s UK home in Spalding, Lincolnshire, and killed Elizabeth Edwards, 49, and Katie Edwards, 13. Afterwards, he walked downstairs and watched the hit movie, Twilight, with his girlfriend, Kim Edwards, who helped him hatch the horrific murder plans.

According to police reports, Kim rationalized the killings by saying she had been suicidal and her mother no longer had to worry about that.

“My mum does not have to deal with me anymore being suicidal, and she does not have to wake up worrying every morning to see if I am still alive. My sister does not have to go through all the heartbreak and like just all the emotions and stuff.”

However, the motive mainly boiled down to jealousy, according to police. While Kim was jealous of her mother’s close relationship with her little sister, Lucas was upset that Katie’s mother was trying to keep them apart. Lucas said he killed the younger sister so she wouldn’t call the police.

“Basically me and Kim… she knew I hated her mum, and I said ‘I wish I could kill her’ and she said ‘yeah’,” Luke told detectives.

The new documentary revealed that although the couple planned a year in advance to kill Elizabeth and Katie, Lucas Markham offered to do the job himself when Kim got cold feet. They were both supposed to commit suicide after the murders, but Kim again, couldn’t bring herself to go through with it.

Elizabeth’s boyfriend, Graham Green, also appeared in the documentary and spoke out for the first time about the incident.

“I think [Kim] is another Myra Hindley as far as I’m concerned. She should never, never, never be let out. They have wrecked my life.”

Det Supt Martin Holvey, who interviewed the teens after the brutal murders, still remembers the hollow look in Luke’s eyes and his cold demeanor as he described how he stabbed Elizabeth in the neck and smothered her, then went to Katie’s room and repeated the same actions.

“Over 30 years as a cop, you look at this case and there’s nothing that rivals it. A really brutal, chilling, cold and callous act that was carried out by these two children on two defenceless victims.”

Both teens received 17.5 years in prison.

[Feature Photo: Family Handout]