On Thursday night, local and state investigators returned to the home and were using infrared light, looking for clues that will tell them whether Sesler first shot his parents and brother, left in the white Thunderbird and then returned to see what he had done. A judge signed a search warrant a few hours earlier.
The new search caps off another day of a fast-moving investigation as Sesler remains on suicide watch at the Waller County Jail. Investigators say they have uncovered enough evidence to believe he was plotting at least one, maybe more than one mass shooting somewhere nearby.
Police say Sesler was a self-described "loner" who cried more than once while admitting to the killing of his mother, father and brother at their Waller home this week.
"This wasn't a fight over a TV show or what we ate for supper. This was something that built up in this guy's head over a significant amount of time," said Waller Co. Sheriff Glenn Smith.
According to court documents, police found bizarre ramblings scrawled on walls inside the home, some of which read, "I love my mom, dad and brother" and "God forgive me because I cannot forgive myself."
His cousin, Robin Warner, told us he continued that theme in a phone call with his aunt.
"He said, 'Oh God will never forgive me for this.' He said, 'I'm so sorry Elizabeth,'" she said.
But authorities believe the situation could have turned even more violent.
"He was getting ready to do some act of violence, which he did carry out on his family, three members being killed," said Sheriff Smith. "Was that the end of it, did that stop, did that satisfy his needs? Things like that will never be known."
"We prevented something horrific from possibly happening. I think I can say that with pretty high confidence," said Waller Police Chief Phil Rehak.
Police tell us they also found an arsenal of weapons -- at least a half dozen rifles and handguns along with a stash of ammunition at three scenes including the house where the murders took place.
Investigators have seized four of Sesler's computers from the house. They tell us they've discovered from them already that he spent considerable time studying serial killers, even grading them, as well as researching mass shootings including Columbine. Police say he was planning some kind of attack.
"Just like grocery stores, mass gatherings, anything else. He has admitted to researching all of that to see what the biggest effect was going to be," Sheriff Smith said.
Investigators say they have not discovered any time or specific location where Sesler planned to go on such a rampage. They tell us he worked up to the murders of his parents here by killing animals including his own pets.
According to police, he's admitted setting fires including some of the wildfires nearby last summer. They say he confessed also to previously shooting at buildings around town after hours including Waller High School. Authorities are investigating those claims.
Folks in town are glad Sesler has been caught.
"I'm glad the law caught him and did their job, you know, before anything happened like that," said resident Jimmy Phillips.
As far as a motive for any of this, authorities say there had been conflict between Sesler and his father, but they wouldn't go into specifics. Police say there have been no other arrests but they are looking into whether he was talking with others about the mass attacks.
We're told Sesler had some part-time jobs, including working as a pizza delivery driver and selling videos on YouTube.
Sesler appeared briefly in court Thursday morning. A judge set his bond at $5 million and ordered an attorney be appointed to him. Mental and physical evaluations on Sesler are already underway, according to Sheriff Smith.
Authorities say they do not have a timetable yet and that the investigation is far from being over.
Even though law enforcement officials say there is no evidence of Sesler having an accomplice, or anyone planning to carry out his actions, Waller ISD is still increasing security at all of its schools today, especially the high school. The district says it is just a precautionary measure.
The Waller County sheriff says he doesn't blame the district for being extra cautious.
"When you have a killer that is admitting to studying Columbine shootings, well obviously that being his school district up the road, Waller should have been concerned and I assure you we are just as concerned," said Sheriff Smith.
Waller ISD says it will continue to be in close contact with law enforcement officials on the Sesler case.
Waller ISD statement that reads in part:
"An extensive investigation is being conducted by the Federal Bureau of lnvestigation (FBl), Texas Rangers, Waller County Sheriff's Department, and the City of Waller Police Department. Law enforcement officials are working diligently around the clock to thoroughly investigate this case, and we are in constant communication with them.
After discussing this safety concern with law enforcement officials who are conducting the investigation and have knowledge of the facts, Waller County Sheriff Glenn Smith and the City of Waller Police Chief Phil Rehak have assured Waller ISD that there is no factual evidence that leads law enforcement officials to believe that there is a safety threat at Waller High School or any campus in Waller lSD. ln addition, they do not have factual evidence that anyone else was conspiring with the suspect to do harm.
I want to reassure the Waller ISD family that the safety of our students, faculty, and staff remains our top priority.
As a precaution, we will increase the visibility of law enforcement throughout Waller lSD.
We will continue to work closely with law enforcement officials on this incident. We are committed to provide a safe and secure learning environment for all of our Waller ISD family."
Waller lndependent School District
If there is any new information about Trey Sesler and the murders, we will bring it to you on Eyewitness News and abc13.com.