It's any parents worst nightmare - the disappearance of your young child.
Now, newly-released 911 calls are raising eyebrows in the mysterious case of Isabel Celis because of her dad's demeanor when he called to report her missing from their Tucson, Arizona home.
When her father, Sergio, discovered she was missing at 8 a.m. on April 21st, he called and said: "Hello, I need to report a uh, missing child. I believe she was abducted from my house."
His voice was calm and even, but what's truly jarring to some is the way he chuckles at the end of the exchange.
Operator: "Is mom there also?"
Sergio: "Uh, she had just left for work. I just called her and I told her to get her butt home," he then began to chuckle.
HLN's Jane Velez-Mitchell said, "There is something strange, very strange about his reaction."
Why would a loving dad chuckle just moments after learning that his six year old daughter was missing?
Velez-Mitchell said, "It is very possible that an innocent person has an eerily calm reaction because they are in shock."
It's quite a contrast to the emergency call made by Isabel's mother. After she returned home, she made her own 911 call.
Mother: "She's only six! Can you please hurry and get somebody over here! Oh my God! Somebody took the window out of our house! Please hurry!"
Four days after she was reported missing, her father was extremely emotional in his plea for his daughter's return.
Sergio said in the plea, "Please, please, to the person or persons who have Isabel- tell us your demands! Tell us what you want! We'll do anything for her! We are looking for you Isa. We love you and we miss you so much, we'll never give up looking for you!"
Cops have said the parents are cooperating with them. But Isabel's dad has voluntarily agreed with child protective services to stay away from his other two children.
Now, the clock is ticking and a little girl is still missing.
Police say they've gotten more than 1,000 tips, but so far, there are no suspects.