(CNN) -- An East Texas man accused of killing his mother, father and brother in what may have been a prelude to a mass shooting -- possibly at a school -- had a penchant for studying the work of serial killers, law enforcement officials said Thursday.
The arrest of Trey Sesler, 22, likely prevented "something horrific," Waller police Chief Phil Rehack said.
"I think I can say that with pretty high confidence," Rehack said in a news conference.
Police arrested Sesler on Tuesday, hours after police discovered the bodies of his family inside their ransacked home in Waller, about 63 miles northwest of Houston. All three had been shot.
Police later recovered six weapons and a sizable cache of ammunition from that home and another at which Sesler had been known to stay, Waller County Sheriff Glenn Smith said.
While investigators have yet to examine computers seized from Sesler's home and car or writings that could shed light on his motives, Rehack and Smith said the man had entertained thoughts of committing a mass shooting similar to the 1999 attack at Columbine High School in Colorado that left 13 people dead.
Rehack said Sesler told investigators during eight hours of questioning that he had studied mass shootings and serial killers "to the point of grading their work."
He also acknowledged killing animals, including family pets, over the years, shooting at vacant buildings and schools in the middle of the night and setting fires, Rehack said.
Smith said it appeared Sesler was "building himself up" for an attack. He may have been planning something for three or four years, the sheriff added.
The law enforcement officials said they do not have any specific evidence that anyone plotted with Sesler regarding a specific attack, but vowed they would continue their investigation for as long as it takes to make sure.
"Because if we've got somebody else out there that's thinking along the lines of what we've seen the last two days that he thinks like, we need to know who it is," Smith said.
School officials said in a statement that they had been told of no evidence of a safety threat at district schools, but planned to increase police presence throughout the district as a precaution.
Why Sesler killed his family remains unclear. Smith said some conflict had been building between Sesler and his father, but added that Sesler changed his explanation for the killings several times during the interrogation. The sheriff declined to offer other specifics.
"He cried some during the admission of what he'd done," Smith said.