A love triangle between a high school teacher and two of her students turned deadly, police said, when one of her lovers allegedly stabbed the other after catching the pair naked in her home.
Sixto Balbuena, 20, a Navy sailor, is being held on a second-degree murder charge in the death of 18-year-old Samuel Valdivia. Both men were apparently lovers of 48-year-old high school math teacher Tamara Hofmann, who taught at El Dorado High School in Chandler, Ariz., where Valdivia was a senior, police said. Balbuena had also been a student of Hofmann's at another school, police added.
Valdivia's family was shocked by his killing, his older brother saying they had no idea he was having an affair with his teacher. The day he was killed, Valdivia was to have played in his first baseball game with the high school team, something he had been very much looking forward to.
"I don't know what happened," Julio Valdivia told ABCNews.com. "I don't have a clue."
According to a Chandler Police Department report, Balbuena was on leave from the Navy when he went to Hofmann's house around 2 a.m. on Friday. He told police that he entered the house after Hofmann, identified in the report as being his fiancée, did not pick up the phone when he called.
Police said Balbuena told them he heard a noise and, fearing for his fiancée's safety, grabbed a kitchen knife and headed upstairs where he saw Valdivia run into the bathroom. The report states that after forcing the bathroom door open and finding Valdivia in there with a nude Hofmann, he began kicking and punching the teen, later throwing objects at him, including a computer printer.
According to the report, Balbuena told police he didn't mean to kill Valdivia; he allegedly said he just wanted to teach him a lesson for sleeping with his fiancée.
When he stabbed Valdivia in the stomach with the kitchen knife, Balbuena reportedly told police, "the blade went in like going into butter."
Balbuena also told police, according to the report, that he threw Hofmann to the floor and demanded to know how long she'd been cheating on him, but he said he never got an answer. According to the report, Balbuena then called 911 and, feeling remorse for what had happened, waited for police to arrive.
Valdivia was pronounced dead at a local hospital.
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Balbuena was being held at the Maricopa County Jail on $100,000 bond. In a statement to ABC 15 in Phoenix, his brother, Alex Balbuena said, "this wasn't like him."
"Everyone always liked him, he never had any bad history," Alex Balbuena said. "No matter where he went he made friends."
Messages left for Hofmann were not returned.
Police are now investigating whether she had a sexual relationship with Balbuena, Valdivia or any other students when they were under 18.
El Dorado Principal Ramona Gonzales told ABCNews.com that Hofmann has been suspended pending the outcome of a police investigation. The school, she said, is also looking into the matter independently of police.
Valdivia, she said, had a good sense of humor and often greeted people in the hallways with a smile.
Counselors, both from El Dorado and from neighboring schools were brought in to speak with students upset by Valdivia's death.
"Samuel was a wonderful young man, so he had many friends," Gonzales said. Julio Valdivia said his brother, younger by one year, was his best friend.
"He was an amazing guy," he said. "Everybody from school would talk to him."
He was also, his brother said, a gifted singer who had made demo CDs, hoping to turn his talent into a career.
When asked about Balbuena, Julio Valdivia said, "I don't want to talk about that guy."
Julio Valdivia, who also had Hofmann as a teacher, said he never had any inkling that she and his brother were romantically involved.
But Chandler police said there was evidence that Hofmann's interest in her students goes back a few years.
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Chandler Police Sgt. Joe Favazzo told ABCNews.com that police found Hofmann and Balbuena together in a parked car back in 2006, but had no reason to charge her.
Balbuena, then 17, was a student at Marcus de Niza High School in nearby Tempe where Hofmann was his math teacher at the time.
"They were not doing anything," he said. "They were dressed."
According to the police report from November 2006, Balbuena initially tried to pass himself off as his 21-year-old brother Wayne. They told police that Balbuena was a family friend of Hofmann's and that the two had stopped on the street to empty an ice chest after attending a soccer game, the report said.
But upon being searched by police, Balbuena was found to be in possession of Hofmann's bra, according to the report. His explanation was that Hofmann had asked him to stow some of her clothes in the back of the car, but neither had an answer for why he was still carrying the bra.
Both were administered breath tests -- Balbuena had not consumed alcohol and Hofmann was under the legal limit -- and Balbuena's parents were called to pick him up. According to the police report, Balbuena's parents did not know he was with his teacher at that time, but that Hofmann had regularly picked him up to tutor him in math.
After the 2006 incident, Chandler police notified Marcus de Niza High School and shared a copy of the report with administrators.
A school district spokeswoman confirmed to ABCNews.com that Hofmann resigned from her job there in May 2007, but would not provide the reason nor comment on whether it had anything to do with the police report.
Jason Rusher, Hofmann's ex-husband, said he tried to warn judges during their divorce proceedings that she had allegedly been having improper relationships with her students.
"They didn't want to listen to me," he told ABCNews.com. "They thought I was nuts."
Their divorce was finalized about nine months ago, he said, and Hofmann's relationship with her students was a factor. Rusher said he had walked in on his ex-wife while she was having sexual relations with Balbuena.
Balbuena is next due in court on Thursday to enter a plea.