'I didn't mean for this to happen': Mother blames self after boyfriend charged in son's death

"They were trying to get his heart to start beating, they couldn't get it they said ,' he's not breathing on his own...'" 

A mother recalls the horror of watching paramedics try to save her 10-month-old son. Detectives now saying he died at the hands of his mother's boyfriend, who is also a registered sex offender.

"He was blue and yellow and the 911 dispatcher said 'you need to proceed with CPR on him,' and I tried," said Rebecca, the mother of 10-month-old Caius Bruner.

Rebecca says no matter how hard she and paramedics tried, she couldn't save her blue-eyed little boy. Her boyfriend, 24-year-old Neil Hicks, is charged in the death and hurting her 3-year-old boy last Wednesday at the family's home on Ray Brown Road.

Related: Sex offender charged with murder of girlfriend's infant son

"This is my child and it was my responsibility and I messed up really bad." 

Rebecca says she was away at work and Ryan was home with the kids. She says she got a call from a friend who told her to get home and check on her sons. The two had known each other for a long time, but had just recently started dating. She says she never knew he was charged with a sex offense years ago when he was 18 and the victim, who Rebecca says was his girlfriend at the time, was 14. 

"I didn't mean for this to happen, I didn't really mean for this to happen."

Rebecca says she trusted Ryan with her children.

"I don't understand, no one understands, even the sheriffs don't understand."

It's unclear how the children were injured. Rebecca says Nick told her that he dropped her son and that he fell off the bed, but she says she believes that is a lie.

Now she just wants the truth from Ryan, the only adult who knows what happened. 

Rebecca says her 3-year-old, who was also injured, is now staying with a family member.

Ryan has been charged with negligent child abuse inflicting serious bodily injury, sex offender using social website and second degree murder. He remains in jail under a $1 million bond.