Ex-UCLA basketball star Billy Knight was arrested back in June after officials say he sexually abused a child ... and sources say the victim was only 9 years old.
TMZ Sports has learned ... in the weeks before Knight apparently killed himself, the 39-year-old was arrested and charged with 6 felonies for sexual encounters involving a girl under the age of 15.
Officials tell us ... Knight was arrested in Phoenix, Arizona on June 13.
Prosecutors in Maricopa County charged Knight with multiple counts of sexual conduct with a minor, sexual abuse and molestation of a child.
In court docs, obtained by TMZ Sports, prosecutors say some of the abuse took place at the victim's home -- and on her mother's bed.
Arizona is particularly tough when it comes to sex crimes involving minors -- and it appears he was facing more than 50 YEARS in prison if convicted on all charges.
Knight posted his $100,000 bail and was released from custody in June -- but ordered to wear an electronic monitoring device.
However, the victim's mother told cops Knight violated the terms of his release by contacting her several times and even appearing at her home.
He was due back in court in the coming weeks.
Knight was found dead in Phoenix in the early hours of July 8 -- after posting a disturbing goodbye video ... in which he admitted to living a life of "sin" and implied he was going to take his own life.