6:49 AM PT -- TMZ Sports spoke with a person from Trent's camp who tells us the NFL star is ADAMANT the neighbor's dog attacked one of his dogs first -- and his dogs only acted in self-defense.
Williams says the neighbor's dog was attacking his daughter's tiny Basenji dog -- a smaller, more fragile dog. At that point, a larger pit bull mastiff came over to assist the Basenji and in the process got a hold of Sandy -- killing her.
We're told as a result of the initial attack, Trent's daughter's dog is hospitalized with serious injuries.
The point Williams is trying to make ... is that his pit bulls weren't running rampant in the neighborhood, attacking random pets, but rather, this was the result of an unfortunate animal altercation.
The person we spoke with tells us Williams is NOT breeding dogs for fighting.
A pit bull owned by NFL star Trent Williamskilled a neighbor's 3-year-old black lab -- and while the neighbor is PISSED -- Williams says it's no big deal.
Linda Flowers says her beloved dog, Sandy, was attacked and dragged through a fence by one of 9 pitbulls at Williams' Missouri City, TX home, ripping its body to shreds in the process.
Flowers tells TMZ Sports ... Sandy was docile and friendly and is clearly the victim in the situation. She believes Williams is running a dangerous pit bull mastiff kennel out of his backyard in a residential community with families and children.
Williams, however, told FOX 5 in D.C. he doesn't understand why the mauling is such a big deal ... saying it's "dogs doing what dogs do."
Williams claims his dogs did nothing wrong -- and it was Sandy who broke into his yard and attacked his dogs first.
We've learned Missouri City PD responded to the scene -- but kicked the case over to animal control, which is currently investigating.
No arrests have been made and no charges filed at this time.
31-year old Williams is a star for the Redskins -- the #4 overall pick in 2010 is a 7-time Pro Bowler and signed a 5-year, $66 million contract in 2015.