Prosecutors say they believe the motive behind the murder of a Maryland high school teacher was a love triangle.

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Tyler Lewis Tessier, 32, accused of killing his girlfriend, Laura Wallen, 31, admitted to police that he was engaged to another woman, court documents show. Both women were aware of each other, however, believed they were dating him exclusively.

The investigation reveals that at the end of August, Wallen sent the following text message to Tessier's fiance:

"It's important that some things are cleared up and I would imagine that if you were in my position, you'd want some answers as well. By no means is this an attempt at confrontation, just looking for an explanation...woman to woman."

Prosecutors believe the love triangle between Wallen, Tessier and his fiance was the probable motive behind the killing. Wallen's attempt to get in touch with the fiance may have also played a role in her murder.

Wallen's best friends were also led to believe that her baby had been fathered by another man. According to court documents, Tessier sent messages to them pretending to be Wallen, stating that she was worried that somebody else was the father.

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Furthermore, one of Wallen's best friends received a series of text messages from her on September 2, court documents show. Wallen sent a text to her best friend saying that Tessier had taken her to a field and she didn't know why. She then sent a picture of the large field with a tree line. Authorities think the picture was of the same field where her body was later found.

Tessier went back to that field at least ten times since Wallen went missing, according to the investigation.

Wallen last contacted her family on September 3, officials said. Her body was found on Wednesday in a shallow grave in the Damascus area.

Tessier, was arrested for Wallen's murder on Wednesday. He is being held without bail.

Read through the statement of charges here:

Tyler Tessier Statement of Charges