"I would like to know why," Cooper's mom, Donna Rentz, said.
Unable to finish her sentence, Rentz tried to find the words the family hopes will reach the ears of the person responsible for Cooper's death.
"I think if they had a shred of decency in their body, they would come forward and acknowledge their guilt," Cooper's father, Gary Rentz, said.
Although Cary Police do not have any suspects and have not named a person of interest, they maintain the killing was an isolated incident and the community is safe.
Cary Police Chief, Pat Bazemore, stated she remains confident the case will be brought to a swift conclusion.
She also stated Friday's press conference would be the last until an arrest is made.
The police did not update the media on what was found in evidence collected from the Cooper's home, car and Cooper's husband, Brad.
Instead, the focus was on 4-year-old Bella and 2-year-old Katie.
Despite instructions from the chief not to ask about the case, one reporter asked the parents how Nancy was acting before her murder. The family seemed to have a difference of opinion.
Nancy's dad said he was not worried, but her mother stated she was worried.
Rentz could not stop talking about her beloved daughter. "Her love and pure joy for life, she had it as a young child until now," she said, crying.
Nancy's youngest daughter, Katie, will turn 2 on Wednesday.
A Wake County court granted custody of the girls to the Rentzs and Nancy's sister, Krista. Krista was not present at Friday morning's news conference, but she is with the children and the girls are reportedly doing fine.
The family stated they have contacted the psychologist that the children's mother worked with in Cary. They want to get a better understanding of how to deal with anything regarding the children and their parents.
A reporter asked the family if the children had been asking about their dad and they answered, "no they have not."
They also stated that they are finding the communication to reporters very cathartic.
According to the family, Nancy's girls call their Aunt Krista, "Krista mum." The family said Krista and Nancy, who are twins, look so similar that it's easier for the children to cope.
Nancy's family is setting up a trust fund for the two girls. More information on how to donate will be released next week.
Friday evening a vigil is scheduled for Nancy, but it is only open to close family and friends.
There will be a second vigil 2:30 - 4:30 p.m. Saturday at the Koka Booth Theatre in Cary. It is open to anyone who would like to share in rememberances to Nancy.
A third vigil is scheduled in Canada next week.
The family said they will take the children to Canada this week and return to Cary next Thursday.