The Early Show national correspondent Hattie Kauffman
Police say his cigarettes gave him away.
"We found DNA from cigarette butts at the scene that matched DNA that came from within the crime scene itself," Napa Police Chief Richard Melton told a news conference.
Both victims were well known in Napa, Kauffman says. Mazzara, a former beauty queen, worked at one of the local wineries that make the town famous. Insogna was an engineer at the Sanitation Department.
From the start, police thought the girls might have known their killer.
It turns out the suspect is the husband of a close friend of Insogna's.
"My understanding," Melton told reporters, "is the close friendship is between Eric Copple's wife and Adrianne Insogna."
Kauffman interviewed Copple's wife last year. At the time she was his fiancée, and grieving for her friend.
Apparently, Kauffman says, she had no idea her then-future husband was a suspect.
"Adriane was one of my best friends," Lily Prudhomme told Kauffman. "We worked together, lived near each other, and worked out at the gym together. She's probably one of the most generous people I have ever met."
Asked who she thought had killed Insogna, Prudhomme said, "I have no idea. Honesty. I have no idea, and if I did, I really couldn't say. It's a huge shock."
Now, a shock of a different type has been dealt to Insogna's family.
"It is just so sad and shocking that the then-fiancé and now husband of my daughter's dear friend, Lily, and my own dear friend, committed these crimes," Insogna's mother, Arlene Allen, said at a news conference about the arrest.
Police say they have a confession from Copple, but they're not saying what his motive might have been.
"My burning question is, 'Why?' " Allen said.
On The Early Show Friday, Allen told Tracy Smith that's what she'd ask Copple if she got the chance to speak with him.
"I would try to find out what it was that propelled him to commit these crimes," she said. "But mostly, I think I would offer up my prayers for him, because I really feel that Eric, at this point in time, would really undo this if he could. I believe that he had a very friendly relationship with my daughter, and I really feel that if there was any way that he could undo it, that's what he would do. So I really wish God's grace on him."
Allen said she was shocked when she was told the name of the person who was arrested.
"I fully expected it to be someone that I didn't know, that came from outside the area," she said, "and when I did hear his name, my first thought was for his wife, Adriane's friend and my friend, and what she must be going through. And my heart was filled with such sorrow for her and for her family. … And I did not sleep one minute that night, thinking about the great sadness and loss that, now, two other families are experiencing in addition to those of us who lost our loved ones."
She described Copple as "very nice, polite, but kind of remote."
Melton told Smith that the department is sure they have their man in Copple.
"We've had admissions," Melton said. "We've had things that were said in the admissions that we had not released to anybody, and then we have other physical evidence, DNA, that we feel … is consistent with what our beliefs are. So we feel absolutely sure that Eric Matthew Copple is the suspect in this case."