GREENE COUNTY, Mo. — The teen who stabbed an elderly woman to death in Greene County has been charged as an adult.

Seventeen-year-old Trystan T. Westrip, of Republic, is facing charges of the first-degree murder of 80-year-old Mary Shisler.

He also faces charges of armed criminal action, first-degree tampering, and second-degree attempted arson. 

Westrip – who was sixteen at the time – has been in the custody of Green County Juvenile since his arrest on October 21, 2016.

Earlier that evening, authorities responded to Shisler’s home on the evening of October 21, 2016, after neighbors reported a suspicious green vehicle in Shisler’s driveway. Shisler’s vehicle was also missing.

A neighbor entered through the back door of Shisler’s home – which was open – and smelled gas accompanied by a gas heater and burner to a stove both turned on. The neighbor turned off the appliances and called the police.

Deputies found a bottle of lighter fluid that had been slashed as well as a match sticking up inside a wad of toilet paper. A small amount of blood was also spotted in the home.

After running the VIN number to the suspicious vehicle, deputies confirmed it belonged to Westrip, who was considered a runaway.

Missouri State Highway Patrol later found Shisler’s vehicle in Marshfield where they found Westrip to be the driver.

Westrip made several comments, saying he killed the “old lady” who they truck belonged to and drug her body into a field near her residence. He was transported to the scene and pointed where he left her body.

Shisler was found dead, having suffered multiple stab wounds to her head.

During a post-Miranda interview, Westrip says he left his home on Oct. 21 after an altercation with his parents. He says he was trying to drive to Canada but later decided his vehicle (the one found in Shisler’s driveway) would not make it that far north.

He spotted Shisler’s truck, stopped, and began speaking with Shisler.

She offered to buy him gas but he refused and they began to walk to the neighbor’s house together. This is when Westrip pulled a knife out of his pocket and stabbed Shisler in the temple at least twice.

He then lifted her body over a fence and into a field to conceal it. Shisler was not yet dead and Westrip stabbed her seven more times in the head.

Westrip then stole items from Shisler’s residence and wished the destroy the evidence. This is when he soaked the toilet paper with gasoline and lit a match. 

After driving away in Shisler’s vehicle, Westrip realized his plan did not work and later stole a firearm from a camp.

A bond for Westrip has not been set.