A Maine teen who stabbed his parents to death and killed the family dog on Halloween morning last year was struggling with his gender identity at the time, the Kennebec Journal reports.

On Friday, a grand jury indicted Andrew Balcer, 19, in connection with the slayings.

The action comes after a judge ruled in November that Balcer, who was nearly 18 at the time of the murders, would be prosecuted as an adult instead of a juvenile.

In arguing that the court should treat Balcer as an adult, prosecutors played an audio recording in which he told a dispatcher that he brutally stabbed his mother and father because he “snapped.” He then killed the dog, a Chihuahua, to stop it from barking.

A potential motive for the murders could be that Balcer was upset over his belief that his parents didn’t support him while he was struggling with his gender identity, according to Judge Eric Walker.

“The only possible motive for the murders appears to be Andrew’s perception that his parents were unwilling or unable to deal with his transgender issues,” Walker said in his ruling that Balcer be treated as an adult.

“We will never know if Antonio or Alice Balcer would have been accepting, because they were ambushed and murdered by Andrew.”

Walter McKee, Balcer’s defense attorney, had sought to keep Andrew Balcer in the juvenile justice system. On Friday, McKee said Balcer would plead not guilty.

According to police, Balcer stabbed his mother nine times with a hunting knife as she was hugging him early Halloween morning in 2016. She screamed, which woke his father, at which point Balcer stabbed him 13 times.

Balcer’s older brother, Christopher, was reportedly in the basement at the time of the killings. Balcer asked him if he wanted to die, and Christopher pleaded with his brother to spare his life. Christopher escaped and ran to a neighbor’s house, according to the newspaper.

“I don’t know what it was about our relationship up to that point that gave me a free pass, as far as the family had been concerned,” Christopher said in a candid February interview with the newspaper.

“I don’t know if how he felt about me was different from how he felt about the parents, but apparently it was.”

People familiar with Balcer have described him as smart but without a social life. His gender identity struggle emerged publicly during a court proceeding in October. Christopher Balcer said he wasn’t aware of the issue and believed his mom and dad would have supported his brother.

Balcer told staff at a youth development center, where stayed for a time since the killings, that he prefers to wear women’s clothes and be called “Andrea.”

Balcer faces two counts of intentional murder and one count of aggravated cruelty to animals. He faces the possibility of life in prison if convicted.

[Feature image: Facebook/Andrew and Alice Balcer]