In a statement, police confirmed that the storage facility where Gavin's car was found has been linked to John Creech, the husband of Gavin's former mistress, Chandrika Creech.
Now, Gavin's sister Tara Smith Addeo is speaking out exclusively about this major break in the case, and the many conflicting, overwhelming emotions it raises.
"I don't think anything really prepares you for news when somebody you love so much has been killed at the hands of somebody else," she tells E! News. "It's tragic when it's an accident, but when you know it's on purpose, it just has a whole new light to it. Where I was beginning to lose hope that Gavin would be found alive, it's still very, very difficult, because you just think that somebody is going to be around forever, that you're going be around all the time....So it's extremely upsetting."
Was she surprised to learn that Gavin's death had been ruled a homicide?
"No," she says. "If you had asked me that eight to ten months ago, I would have said yes. I had no reason to believe that it was foul play...I can't believe he would have walked away from his kids on his own. So in the back of my mind, I kept thinking maybe it is possible that something bad has happened to him."
Still, nothing could have prepared her for the painful, vicious reality once police confirmed that foul play was suspected in Gavin's disappearance.
"I don't think you ever can brace yourself for it or prepare yourself for it," she says, before eventually breaking down.
"Having somebody taken from you in any matter is awful and its tragic," she says through tears. "But when you know they didn't have to die...It just gives this whole new dimension of feelings because you can't understand why anybody would take somebody else's life."
Her hope now, she explains, is that "by finding the car, [police] have enough evidence to prosecute every single person responsible for Gavin's death."
As for John Creech, Tara says she recalls hearing his name before Gavin went missing.
"I had heard it because of Johnny's wife, Chandrika—that is how I knew of Johnny," she says, claiming that it was Gavin's wife, Lisa Smith, who first mentioned John's name.
Tara also confirms that both Gavin and Chandrika were romantically involved. "Yes, Gavin and Chandy did have a relationship several years ago—two, three years ago," she notes. "They met through some organization, so they were connected together and that is how I heard about the link with Johnny."
However, Tara alleges that Gavin never opened up to her about Chandrika's husband.
"No. Gavin never spoke with me about Johnny. I never heard Gavin mention John's name before, ever," she insists.
"It is difficult because none of us are perfect, and Gavin struggled with that," Tara adds, looking back on her brother's affair. "And I just feel like everybody has something that they are not exactly proud of."
Tara search for answers—and her desire to speak out about her brother's disappearance—was prompted by one key factor.
"I think I have been motivated by finding answers for my nephews," she says about Gavin's sons. "They are very special boys, and I know that if my brother were here, were it the opposite [situation], my brother would do the exact same thing for my three daughters. He would never ever give up until he had answers if something happened to me."
And despite the scrim of tragedy that's now been pulled over her brother's memory, Tara also wants people to remember the kind, compassionate person she always knew Gavin to be.
"I want people to know the type of person Gavin was," Tara says. "And how much people loved him and cared about him and what an integral part of our family he was."
"Gavin was an amazing brother," she adds. "He was an amazing father and he was an amazing man. Just growing up with him was pretty special...I am not going to rest until I have justice for Gavin."
For more on the Gavin Smith case, watch E! News tonight at 7 p.m. and 11:30 p.m.