A MAN who allegedly murdered his girlfriend after discovering she was leaving him to attend college, also sent text messages to her family telling them he had killed her.

Authorities say Gabriel Glen Navarro, 20, of Washington state in the northwest United States, is being charged with first-degree murder of his girlfriend Allison Leedy, also 20.

Leedy planned to leave Mr Navarro after three years together, to move to California to study, according to the Daily Mail. Prosecutor Adrienne McCoy described the couple’s relationship as one characterised by “manipulation, isolation and psychological destruction”.

In court documents, it is alleged Mr Navarro was “determined to prevent Allison and her family from realising her dreams”.

Authorities say Mr Navarro strangled Leedy in the apartment they shared, before texting members of her family, including her father and younger sister. “If you are getting this you are responsible for Allison’s death,” he wrote. “You turned her against me.”

He then allegedly sent a text to her father that read: “She’s dead. I have the last laugh.”

After calling emergency services to report Leedy’s murder, Mr Navarro allegedly lied to police, telling them he had created a trap of exploding gas in his apartment and also that he was armed with a gun. He surrendered after police surrounded the building.

“One of our concerns ... was that maybe a lot of this was an effort to get us to the point where we’d feel that to deal with the threat, we’d have to shoot him,” said a police spokesman.

After he was arrested, Navarro reportedly told police that his alternate personality, “Frost”, had killed Leedy.