Trent Williams has been slapped with a demand letter to get rid of his 9 pit bull mastiffs after his neighbor's dog was mauled and killed last week ... TMZ Sports has learned.
The NFL star's Missouri City, TX neighbor is threatening a lawsuit after her 3-year-old black lab was dragged through her backyard fence and ripped to shreds on Wednesday.
Authorities are currently investigating the dog's death -- as well as the circumstances surrounding the incident -- and Linda Flowers' attorney says they're hell-bent on getting justice.
"Right now we're hoping the authorities handle it," John Kovach tells us. "If the authorities don't handle it, that's when I come in and my firm will handle it."
"In the lawsuit, I'll seek an injunction that restrains him from having those dogs at his house."
Williams claims it was Flowers' dog that initiated the attack, but Kovach says the evidence doesn't back up his claim.
Williams also addressed the incident with local reporters last week ... saying it was "dogs doing what dogs do."
TMZ Sports has obtained the 911 call Flowers made after the incident ... and it's very emotional.