WALLER, Texas – A 22-year-old Waller County man suspected of murdering his parents and older brother confessed to investigators　Wednesday that he was planning a much larger, Columbine-style attack at a local school when he opened fire on his family, law enforcement sources confirmed to KHOU 11 News.

Trey Sesler reportedly opened up to investigators at the Waller County Jail, where he’s been held since his arrest Tuesday evening.

According to investigators, Sesler said he killed his parents and brother because he didn’t want them to be ashamed of what he was about to do.

He said he’d been shooting livestock to build up courage for a Columbine-style mass-shooting at a nearby campus. Investigators did not say what school Sesler allegedly had in mind.

Sesler posted videos of himself firing weapons on YouTube prior to the triple homicide, and investigators said they were working to determine if he had any supporters or accomplices in his activities.

Sesler was arrested Tuesday night, just hours after police found the bodies of his parents – Lawton Ray and Rhonda Wyse Sesler – and his brother, 26-year-old Mark Alan Sesler, at their home in Waller.

Police are not sure exactly when the victims were shot, but said it could have been as early as Monday afternoon. Police were called to the home by concerned family members around 1 p.m. Tuesday.

Investigators described the gruesome scene as a "war zone."

"The best way for me to describe the residence is it looked like a war zone – a tremendous amount of damage inside the residence, the crime scene was not contained to one area of the residence. It was from one end of the residence to the other, front to back, which is unusual," Waller Police Chief Phil Rehak said.

Texas Rangers quickly tracked Trey Sesler down at a friend’s house near Magnolia after spotting his car outside the residence. They said he had several guns on him at the time.

Family members said the young suspect was suffering from some type of mental illness.

But investigators on Wednesday said they have no idea what exactly might be wrong.

The FBI was called in Wednesday to assist with the investigation.