[Kaye:] Joshua Komisarjevsky, convicted in a brutal home invasion in Connecticut, was sentenced to death just a short time ago. In 2007, he and another man raped and killed Jennifer Hawke-Petit, then tied up her two daughters and set the house on fire, leaving them to die. He now joins his accomplice, Steven Hayes, on death row. The only survivor of the attack, Dr. William Petit, said in court today, I lost my wife and my home, my wife, my friend, my partner. We were robbed of this in a heinous manner for what? Money. So why did Komisarjevsky do it? I got some insight when the murders first happened back in 2007 from one of Komisarjevsky's friends. A hint of violence. A disturbing prediction of what might come buried in this letter from prison.
[Unidentified Female:] I need someone like you who knows a little about my past to keep me grounded in the future when my criminal demon starts to wander.
[Kaye:] Days after the attack, we interviewed this woman who told us she was a close friend. She asked us not to show her face, but shared the letter he says he sent her from prison years before.
[Unidentified Female:] Prison was a hard pill for me to swallow. There isn't a day that goes by that I don't get angry. There isn't a day that goes by that I don't feel the pain of being taken from my daughter.
[Kaye:] He writes about his dreams of becoming a real estate developer.
[Unidentified Female:] My daughter needs me and I can't accomplish my goals when I am locked up.
[Kaye:] Police say Komisarjevsky followed Mrs. Hawke-Petit and one of her daughters home from the grocery store in July 2007 and chose them as his next victims. Neither suspect has ever been arrested for murder before, though they are hardly strangers to crime. In fact, between the two of them, they've been arrested nearly 50 times. On Hayes' rap sheet, 27 arrests, including illegal possession of a firearm, burglary, and forgery. Komisarjevsky's past is just as ugly. Twenty arrests for burglary and larceny. Police say he sometimes used night vision goggles. Both have served time in prison. But it was here at the Silliman halfway house in Hartford, Connecticut, where they first met. They were roommates for four months. What might have driven them to sexually assault and strangle Jennifer Hawke-Petit and leave her two beautiful daughters to die in a fire they had set? Forensic psychiatrist Helen Morrison has studied cases like this.
[Helen Morrison, Forensic Psychiatrist:] It appears that both of them were really consumed with rage at the unfairness of their lives, so to speak.
[Kaye:] Komisarjevsky was adopted as an infant. His grandfather was a leading Russian theatrical director and the son of a princess. His grandmother, a well-known modern dancer. A family friend told us his parents, born again Christians, had trouble controlling him. His friend told us that just five days before the murders, Komisarjevsky was distraught over a breakup.
[Unidentified Female:] He was really, really depressed.
[Kaye:] She said, if he did kill Jennifer Hawke-Petit and her girls, something snapped.
[Unidentified Female:] He put the terror into these poor girls hearts and he was the person that they spent their last hours in fear for their lives. And he left them to burn.
[Kaye:] A senseless act, not even a history of crime can explain. Now let's go straight to the Connecticut court where Komisarjevsky was sentenced. Our Brian Vitagliano is there. Brian, I covered this story, as you just saw there, you know, all those years ago. It was so disturbing. So I can hardly imagine what that atmosphere was like in that courtroom today. Can you tell us?
[Brian Vitagliano, Cnn Correspondent:] Yes, Randi. Hi. Yes, the courtroom ran high with emotion. Obviously it was a very somber hour and 45 minutes. Joshua Komisarjevsky at 10:00 a.m. was led into courtroom in an orange prison jumpsuit and shackles. He had to sit there and listen to Jennifer Hawke-Petit's father, and mother, and sister speak via video for victim impact statements. And then Dr. Petit got up and spoke. And it was extremely, extremely emotional. Afterwards, Dr. Petit and the entire Petit family and friends left the courtroom. They did not want to hear anything that Joshua Komisarjevsky had to say. And he did, in fact, speak for roughly about eight minutes. He said that he, quote, "was honest in my confession, then and now." He knew that the result is the same one that they that he did it and he was going to spend his life in prison. He didn't want those innocent women to die. And he didn't need 12 people to tell him what his motivation was. So, I've covered the Steven Hayes' verdict as well and it was extremely emotional. When you sit in court and listen to a judge basically say your fate is now in the hands of others, may God have mercy on your soul, it's extremely powerful.
[Kaye:] Do you think the family you know, I don't like to use the word closure, and I know Dr. Petit certainly didn't, but this is sort of finally coming to an end for them. How much would you say that means to this family?
[Vitagliano:] I think it means a lot. I mean they have they've had to endure two trials now and sit through evidence and sit through horrific testimony about what happened to his wife and seventeen year old daughter and 11 year old daughter. And see photographs of the remains of charred and burned bodies. And it's just you know, that is taxing on anyone. And, you know, during last October, when Dr. Petit came out, someone asked him about closure and he says, quote, "it's not clear to me that time heals all wounds, but you form some form of scars." So, you know, there is a sense that he's moving on. He just recently did get engaged over the holidays. So, you know, he seems to be moving on. But this, by no means, will ever be forgotten for the family or the people of Connecticut, in Cheshire.
[Kaye:] Yes, certainly not. Not a crime that brutal. Brian Vigtaliano there in court for us in Connecticut. Brian, thank you. We've been talking about the impact of concussions all week. Coming up, we'll explain how brain injuries are detected. Dr. Sanjay Gupta is even going to put me to the test. Really?
[Dr. Sanjay Gupta, Chief Medical Correspondent:] I am.
[Kaye:] All right.
[Gupta:] I'm here for it.
[Kaye:] You'll see it live, next.