INSIDE EDITION's Interview with Casey Anthony's Former Fiancé

Casey Anthony's former fiancé, Jesse Grund, spoke exclusively to INSIDE EDITION about his relationship with Casey and finding out he was not Caylee's father.

Casey Anthony's former fiancé knows her unlike anyone else. Jesse Grund was engaged to Anthony long before she was accused of killing her young daughter Caylee.

"It was a very, very close relationship between the two of us," he told INSIDE EDITION's Paul Boyd in 2008.

Grund and Anthony were both working at Universal Studios in Orlando when they began dating. When she became pregnant, she told Grund the baby was his. He played the part of doting dad even after a paternity test proved without a doubt that little Caylee was not his daughter

"It didn't change [our relationship] at all. I got over there and Casey was crying, hold Caylee, and I told her it didn't take blood to be a father and that I was still going to be a father to Caylee and I was still going be the man in her life," Grund said.  

Grund told Boyd he was so enamored with his new family that he proposed to Anthony.   

He said, "I felt like I didn't need anymore time to know that I wanted to spend the rest of my life with her."  

But a few months later the relationship fell apart.

"She started acting kind of weird, a little sketchy, started being really sensitive about the way I was with Caylee," Grund said.

After they broke off the engagement Grund started noticing big changes in his ex-fiancée.

He said, "She went from being someone who was focused on being a mother, starting a family, being a family oriented homebody, to an individual who loved the party, loved the social life, loved to be the person who was at the center of everybody's attention."

"Why the change?" asked Boyd.

"That's a really good question," said Grund. "There's something that happened between old Casey and new Casey. I don't have any idea."

He says he can't believe that the woman he once loved is the same person at the center of the murder trial that's captivating the nation.

"The person that's sitting in jail is not the same warm, kind, loving person who sat in my parents' house and had dinner with us, and sat on football Sundays and played with Caylee, and went to theme parks with," he said.

"Do you believe Casey killed her daughter?" Boyd asked.

"The person that sits in jail, I don't know what she's capable of, I don't know her," said Grund.

He wept thinking about what happened to Caylee.

"Part of me is very sad, and part of me is very angry, and the other part of me wishes I could have done something, but there's nothing I could have done and that's probably the hardest part of this whole thing, loving her like a father and not being able to protect her," he told Boyd.