A teenager in Milwaukee, Wisconsin, is accused of choking his grandmother to the point of her passing out and ultimately dying.

A 15-year-old boy who Law&Crime is referring to as E.B. is charged with first-degree intentional homicide, court records show. The suspect was not originally charged as an adult, local Fox affiliate WITI reported, but that changed on Monday as he made his first appearance in adult court.

The preliminary cause of death for the suspect”s grandmother – 68-year-old Elizabeth Totsky – was strangulation, according to a criminal complaint obtained by Law&Crime. She was found unresponsive on Aug. 27 at about 2:15 p.m. at a home on the 1700 block of Oak Street in South Milwaukee and rushed to a nearby hospital.

E.B. strangled his grandma from behind “by using his right arm and elbow to apply force to her neck for approximately 5 minutes,” he admitted to South Milwaukee Police Department officers, per the complaint. “The defendant stated that during the strangulation, his grandmother struggled with him, and struck him once in the head.”

He only “released his choke hold when he felt his grandmother’s body go limp,” the court document added. Totsky regained a pulse at her home as first responders gave her lifesaving treatment and then put her in an ambulance – but she died days later on Aug. 31.

E.B. was there when police first arrived to the scene – and he gave an account of what happened from the beginning. However, investigators reportedly started to find inconsistencies in his story.

According to the complaint, an officer who arrived quickly at the scene “observed victim Elizabeth Totsky laying on the kitchen floor receiving emergency medical treatment from the South Milwaukee Fire Department.” It was just the grandmother and grandson at the home before E.B. called 911 and first responders arrived.

The teen is said to have told this officer that he and his grandma were in the kitchen cooking eggs when she had a seizure and he “watched her fall to the ground.” He confirmed that it was just the two of them at home at this time.

When the medical examiner conducted an autopsy, however, she “observed evidence of strangulation” and hemorrhages. Then investigators spoke to Totsky’s husband, who had left for work the morning of the incident and arrived home when he was told his wife was hurt.

He also recounted an incident from about two months earlier.

The victim’s husband said that on that day, “he arrived home from work and Ms. Totsky appeared to be shaken up, or disturbed.” The man added that “Ms. Totsky told him that she was bothered because during the day, the defendant had snuck up behind her and placed her into a choke hold, using the crook of his below to strangle her.”

The grandmother reportedly told her husband that “she had lost consciousness for a short period of time and woke up on the floor and observed the defendant standing over her.” He also said his wife, himself, E.B., and the boy’s older brother lived at the home together. This man was the step-grandfather to the two brothers.

E.B. was subsequently arrested and interviewed, again. This time, he said that while his grandmother was cooking, he was in his bedroom, according to the complaint. At some point he left his bedroom to use the bathroom “and smelled something burning in the kitchen, so he went downstairs” and saw his grandma on the floor.

The investigator “noted that this was a different narrative from what the defendant had initially” said, when E.B. “stated that he was in the kitchen and observed his grandmother have a seizure and fall to the ground.” When this detective subsequently told E.B. that the autopsy indicated his grandmother’s cause of death was strangulation, his confession reportedly came out.

It is unclear what investigators believe the teen’s motive – if he had any – was for the crime.

E.B. is scheduled to have a preliminary hearing on Sept. 17.