Murder Victim's Sister Wants More Answers in New Doc 'The Cheshire Murders' [Exclusive Video]

Yahoo! TV

In the summer of 2007, Dr. William Petit; his wife, Jennifer Hawke-Petit; and their daughters, Michaela, 11, and Hayley, 17, were held hostage in their Cheshire, Connecticut home by ex-cons Steven Hayes and Joshua Komisarjevsky. What followed was a horrifying series of events that ended with rape, arson, and a triple homicide, with only Dr. Petit surviving the attack.

Now six years after the tragedy, HBO is exploring the brutal crime that devastated the quiet town of Cheshire and shocked the nation. In this sneak peek at the upcoming documentary, "The Cheshire Murders," it's clear that — even though Hayes and Komisarjevsky were both sentenced to death — the case is not closed for Cindy Hawke-Renn, Hawke-Petit's sister, who still wants answers.

[Related: 'The Cheshire Murders' Filmmakers Examine the Brutal 2007 Petit Family Murders in New HBO Doc]

"I'm a very detective-like person. I like to know details, and until I know the details around things, it's hard to figure things out," says Hawke-Renn. Her biggest questions revolve around what she sees as baffling and unsettling failures by the police department. "I would like to know why my sister and Steven Hayes weren't stopped at the bank, why she wasn't held at the bank." Hayes took Hawke-Petit to the bank shortly after the break-in. She withdrew $15,000 and notified the clerk that her family was being held hostage.

Hawke-Renn also can't comprehend why, when surrounding the Petit's home, the officers didn't act more aggressively. "There were some police officers that, off the record, said to people in the town that they heard the girls screaming in the end. Did they try to enter? Did they not try to enter? And why weren't there policemen looking in the windows. My sister had no blinds on her windows. I just want the facts."

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To learn more about this crime and watch exclusive interviews with the friends and families of the victims and murders — as well as attorneys, journalists, and mental-health professionals involved in the case — tune in to "The Cheshire Murders" on Monday, 7/22 at 9 PM on HBO.