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 14.
Prosecutors in Maricopa County charged Knight with multiple counts of sexual conduct with a minor, sexual abuse and molestation of a child.