JANESVILLE, Wis. -- The wife of the prime suspect in a Janesville triple-homicide case filed for divorce Thursday afternoon.

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Nancy Koepp divorced James Koepp, her husband of seven years and the man identified by the Rock County sheriff as the prime suspect in the homicides.

Danyetta Lentz and her two teenage children were found slain inside their mobile home on Jan. 12.

Nancy Koepp said she divorced her husband because he admitted to having an affair with Lentz, their neighbor.

Nancy Koepp spoke with WISC-TV about her life since the homicides and her thoughts on James Koepp's innocence.

"In my heart, I just can't see it being him. I just can't," Nancy Koepp said. "I just can't believe with his personality, the person that I knew for the past seven years could ever kill anybody, and especially two children, because he absolutely adored his grandbabies."

Nancy Koepp said that James Koepp was acting strange the night before he was arrested. She said that he even called her son with an odd favor.

"And he said, 'Please tell your mom how much I love her. And when this is done and over with, please tell her, let her know that I love her so very much.' And then he hung up," Nancy Koepp said. "And then he called his brother and said, 'I did something really, really stupid. My life is done with. Nancy's going to leave me.'"

Nancy Koepp said she believes James Koepp was referring to an affair he was having with Lentz, something about which he openly talks in his letters to his wife from jail.

"He just keeps telling me that he's so sorry, that he doesn't know why he turned to another woman. One thing led to another. He used to meet her at the mailbox. He fixed her window," Nancy Koepp said.

But when it comes to the killings, Nancy Koepp said she believes her husband is innocent and that he was merely an easy target for investigators.

"Me, personally, I think because of his past, and being a registered sex offender, that they targeted him. And he had an affair with the wrong person, who was in the wrong place at the wrong time," Nancy Koepp said.

A few other family members of James Koepp spoke with WISC-TV, and they also said they believe he is innocent.