Karlie Tyrell spoke to Channel 7's Sunday Night, and it was the first time the heartbroken mother has spoken about what she thinks happened to her son since his 2014 abduction sparked the nation's biggest manhunt.
Karlie told journalist Melissa Doyle that she felt like 'the worst mum in the world' and had isolated herself from her family and friends.
The tearful mother also revealed she believes William is still alive and 'whoever has him needs a bullet.'
"Don’t hurt him. Just let home come home. He hasn’t even met his little brother yet. That’s not fair, it’s just not fair," she said through tears.
Karlie also revealed how many believed she was somehow involved in William's disappearance, but broke down and cried 'no' when asked if she was involved.
When asked what she thought had happened to William, Ms Tyrrell said she didn’t like to speculate, but believed he was out there somewhere.
"Where else could he be?' she asked. 'I feel like whoever has him needs a bullet."
Ms Tyrrell broke down crying and even made her interviewer tear up when she sent a message to William through the camera. "I love you so much. I miss you," she said through tears.
Karlie also broke down admitting she had made 'bad choices' in the past. Some of which eventually led to William being removed from her care.
"I wasn’t ready, I guess. I wanted to do everything I could to be the best mum I could be. So I did everything and yeah, I’m still trying to do everything I can. But I don’t know what else to do," she said.
Ms Tyrrell also expressed her wish to reunite her family, saying: "I want this to end and William to come home."
Karlie has two more children with William's biological father, Brendan Collins.