In a letter to a judge, included in court documents submitted ahead of his sentencing on gun charges, Charles Tan gave his side of the story in his father’s murder, as Tan faces decades behind bars.

Tan was never convicted of charges in his father’s death in Pittsford in February of 2015. However, last year he was arrested and later plead guilty to gun charges related to the purchase of the weapon used in the shooting.

In the letter, referring to the murder, Tan says he felt he had no other choice because he feared his father would kill his mother.

“I told him that he couldn’t put his hands on her, he snapped,” Tan explains, referring to an incident where he says his father nearly choked out his mother, a fight Tan says was the couple’s worst. “He told me to mind my business, and if she pissed him off again, he’ll kill her.”

In the next paragraph, Tan says he acted on impulse.

“I felt like there was no other option, that I had to protect her,” Tan writes. “Rather than digest the situation, and any other possible alternatives, I acted on impulse, leading to my series of immature and irrational decisions.”

After charges were dropped, Tan said he has “taken full advantage of the second chance [Judge Piampiano] has given me.”

He says he started doing volunteer work and returned to college before his arrest on gun charges. Tan says he wants to work with kids and open an after school facility.

“All I need is the opportunity to do so,” Tan pleads at the conclusion of his letter.

In court papers last week, prosecutors are calling for Tan to receive the maximum sentence, 25 years behind bars.

Tan is set to be sentenced on November 19.

Read the full letter by Tan here