Boyfriend of pregnant Maryland teacher indicted on murder charge

The boyfriend of a pregnant teacher found dead in a shallow grave in Montgomery County was indicted on one count of murder.

Tyler Tessier is accused of killing Laura Wallen, a 31-year-old Olney woman who taught social studies at Wilde Lake High School in Columbia. Wallen disappeared in September after her family reported her missing on Labor Day.

Over a week later, Wallen's body was found in a shallow grave at a secluded field in Damascus. Wallen's autopsy revealed that she was shot in the back of the head.

RELATED: Autopsy: Slain pregnant teacher Laura Wallen was shot in back of the head

Tessier, who is the father of Wallen's unborn child, was later arrested after her remains were found. Wallen was four months pregnant when she was killed.

Authorities said they believe the motive behind Wallen's murder was connected to a love triangle between Wallen, Tessier and another woman Tessier was engaged to be married with.

Tessier is scheduled to appear in court for a preliminary hearing Friday morning.

FOX 5's coverage on the disappearance and murder of Laura Wallen:

Autopsy: Slain pregnant teacher Laura Wallen was shot in back of the head

Laura Wallen's murder linked to love triangle, police believe

Letting Tyler Tessier speak at Laura Wallen's news conference part of police strategy

Body of missing pregnant Maryland teacher found; boyfriend arrested

Missing pregnant teacher's family offers $25,000 reward

Vehicle of missing pregnant Maryland teacher found in Howard County

Students coming together to help in search for missing pregnant Md. high school teacher

Wilde Lake High School students hoping for safe return of missing teacher Laura Wallen

Search continues for missing pregnant Maryland teacher

Police searching for missing pregnant Maryland teacher