GONZALES — Two different pictures emerged Friday in the murder trial of a youth accused of fatally stabbing a St. Amant High School senior hours before his homecoming dance in 2015: the inscrutable killer of a high school choir boy or a then-16-year-old defending himself against a larger aggressor.

What is not in dispute is that Jacob Westbrook, now 19, stabbed Todd "T.J." Toups Jr., 18, once in the chest on the afternoon of Oct. 10, 2015, landing a single fatal thrust that pierced the teen's heart and ended a young life after an encounter that lasted just minutes.

According to testimony from emergency responders and a 911 recording played Friday, Westbrook first admitted to a dispatcher and later an arriving deputy - as Westbrook held the head of the wounded Toups while he lay on the ground surrounded by onlookers - that he stabbed Toups.

Westbrook, who claims self-defense, is being tried as an adult and faces a second-degree murder charge and possible life sentence if convicted.

More than three years old, the case has been under a gag order and featured attempts by Westbrook's attorneys, unsuccessfully, to move the case out of Ascension amid their concerns about the pretrial statements of then-Sheriff Jeff Wiley.

Westbrook has also sued the Sheriff’s Office over allegations he was raped while in parish jail and was not sequestered properly as a juvenile judge had directed deputies in the weeks after the slaying.

Perhaps the most emotional moment Friday came when Assistant District Attorney Joni Buquoi played an eight-minute 911 recording for jurors.

Answering a concerned dispatcher through most of the call, Westbrook could be heard directing the application of pressure on Toups’ stab wound as he lay in the gravel next to a trailer house and reporting on the breaths of the unconscious teen with an ebbing pulse.

“He’s right here,” Westbrook told the dispatcher early in the call. “He’s not doing well.”

As the recording was played, Toups’ mother, sobbing, left the courtroom for a time while another family member bawled in someone’s shoulder. Wet eyes were visible elsewhere in the courtroom.

Through other parts of the first day, both sides tried to establish, with testimony that was contradictory at times and hindered by faulty memories, what exactly happened and which youth was the true aggressor.

In opening arguments, Buquoi, the lead prosecutor, told jurors that Westbrook inexplicably stabbed Toups in the upper chest after starting a fight amid an otherwise easygoing visit by Toups to the trailer home of Westbrook's girlfriend hours for the St. Amant dance.

Toups, a school choir member, was coming off a recent breakup from his longtime girlfriend and was at the home to give a ride to one of Toups' fellow choir members, the then-14-year-old stepsister of Westbrook's girlfriend. Toups had met with the girl’s parents a few days earlier about the coming evening.

As Buquoi recounted the details, she told jurors she could not offer them a motive for the slaying but urged them to focus on facts that prove Westbrook's "specific intent" to kill or cause great harm to Toups.

"Sometimes senseless things happen and they're just that, senseless things," Buquoi said at the parish Courthouse Annex in Gonzales.

Later, defense attorney Jarrett Ambeau cast Toups as itching for a confrontation with Westbrook while trying to discreetly take the 14-year-old girl on a date to homecoming, not just offer her a friendly ride. In the days leading up to homecoming, Toups had an exchange at school with the girl’s protective, older step sister in which she threatened to stab him if he harmed her younger sister.

By the time of homecoming afternoon, Ambeau said, Toups was at the trailer hours early and antagonized Westbrook's girlfriend inside her bedroom so Westbrook would come out of that room. Toups then took off his tie and squared up to fight Westbrook, who was 30 pounds lighter than Toups, even after Westbrook had gone to get a knife, Ambeau said.

"Todd is the aggressor. He's picking a fight," Ambeau said.

Holding his fists up and motioning them from a fighting stance, Ambeau compared the two youths to boxers where one had a significant size advantage. Moments after Westbrook tried to drop his hands and the knife believing the moment was over, Ambeau said, Toups punched Westbrook and, in reaction, Westbrook made the fatal swing of the knife.

In later testimony, Erica Whatley, the 14-year-old whom Toups was going to pick up that day, gave a different account. She said Westbrook pretended to shake Toups’ hand inside the trailer after leaving the kitchen and then suddenly stabbed him with the other hand. Toups, who Whatley said didn’t see the knife, stumbled out with the weapon in his chest and fell down outside.

When questioned about a series of subsequent statements as well as texts of hers that appeared to contradict her account, the 17-year-old testified she also could not remember many aspects of the incident three years later.

Yet, she disavowed part of a written statement she made shortly after the slaying in which she claimed Toups and Westbrook were in a fight. Whatley told prosecutors she was under pressure from her mother who told her, “Jacob was family,” and they had to protect him.

A deputy who supervised the youth writing the witness statement testified later he did not notice any parental interference in the writing of that and two other statements from other child witnesses.

Toward the end of the day, jurors heard the recorded statement of Carlee Duplessis, who watched the fight from the trailer door.

Duplessis was Whatley’s then neighbor in Cobb’s Trailer Park and had been working on her friend’s hair for homecoming before Toups arrived.

Once Toups was invited inside, he asked Jacob’s girlfriend in the bedroom - the stepsister - if she was going to stab him. Duplessis said Jacob got up and said, “I will.”

Westbrook went to get the knife in the kitchen. The boys squared off in the trailer, Duplessis said. She told a detective that Westbrook tried to swing the knife, Toups pushed and then punched Westbrook and then Westbrook stabbed Toups.

She described the shocked Toups a moment later.

“‘I was just joking with you, dude,’” Duplessis told the detective Toups saying.

Judge Jason Verdigets of the 23rd Judicial District Court has scheduled testimony to resume 9 a.m. Tuesday.

Follow David J. Mitchell on Twitter, @NewsieDave.