(CNN) -- For three weeks, Dr. William Petit went to a courtroom and re-lived the day he was attacked and his wife and daughters were killed in their Connecticut home.
He calmly testified about being beaten awake from a nap and being taken to his basement tied up, not knowing what was happening to his family upstairs. He rarely left the New Haven courtroom, once excusing himself when a medical examiner testified. He listened stoically Tuesday after one of the accused was found guilty of capital murder.
Now Petit will go through it in court all over again. Steven Hayes' penalty phase is ahead, and a second defendant will face trial afterward.
"People keep asking that question, why do you do it or how do you do it," Petit said after Hayes' verdicts were read Tuesday. "... I think that you probably would all do the same thing for your families if your family was destroyed by evil."
Hayes, 47, was convicted on 16 of the 17 charges against him in connection with the deaths of Jennifer Hawke-Petit and her two daughters, including nine counts of murder and capital murder and four counts of kidnapping. The jurors acquitted him of an arson charge in the burning of the family's home.
The killings of Hawke-Petit, 17-year-old Hayley Petit and 11-year-old Michaela Petit happened in the New Haven suburb of Cheshire on the morning of July 23, 2007. Prosecutors said Hayes and co-defendant Joshua Komisarjevsky entered the home the previous night, beat and bound Petit and attacked his wife and daughters before setting their home on fire. Komisarjevsky, 30, will be tried separately, and prosecutors are seeking the death penalty for Hayes.
Petit and other family members -- including Hawke-Petit's parents, who'd come up from Florida -- attended every session of Hayes' trial, which began September 13. Petit indicated he would attend Hayes' penalty phase, which begins October 18, and Komisarjevsky's trial.
Being in the courtroom every day with the rest of his family was the one thing Petit felt he could do about that day in 2007, he told reporters Tuesday.
"Do I look forward to the ride every day? No," he said. "I have a little nausea every time I get off the exit ramp, [and] a little nausea every time I get out of the car and walk across the street. I think I do it for my family, but I think all of you ... would do the same thing for your families."
Petit, an endocrinologist, testified on September 14 that he had fallen asleep in his home's sunroom as his wife and daughters were watching television July 22, 2007. He awoke as blood ran from a gash on his head, he said.
"I sort of awoke in a daze. ... The next thing I knew I was seated on the middle of the sofa, with my head down [and] there was something warm running down the side of my face," he testified.
Petit testified that the attackers told him to lie down on the couch "and tied my hands at the wrists and my feet at the ankles" and covered his head with a piece of fabric. He was told he'd be shot if he moved, and eventually he was led to the basement, where he was tied to a pole by a rope around his chest and waist, his hands still bound with plastic zip ties, he testified.
Prosecutors said Hayes took Hawke-Petit to a bank, where she withdrew $15,000. She was eventually found inside the home raped and strangled, authorities said.
The attackers tied the girls to their beds and put a pillowcase over their heads, prosecutors said. After getting the money from the bank, the attackers set the home on fire and fled, prosecutors said.
Inside the home, the two daughters, one of whom had been sexually assaulted, died of smoke inhalation, authorities said.
Before the fire, Petit was able to untie the rope on his hands and break the plastic ties, but couldn't undo his feet. He said he heard "three loud noises, like someone was throwing 20- or 30-pound sacks on the living room floor."
Petit testified he heard a "whoosh" sound shortly afterward. Fearing for his family's safety, Petit, still bound by his feet, hopped up his basement steps, left the home and headed for a nearby house, where he alerted a neighbor and asked him to call 911.
Prosecutors say the attackers put gasoline in several plastic gallon-size jugs found at the house to start the fire in the home.
During Hayes' trial, jurors were visibly stunned when they were shown pictures of the victims' burned remains, and at least one wept.
Helen Ubiñas, a Hartford Courant columnist who covered the trial, told CNN that the testimony and evidence made the trial "an incredibly grueling ordeal for the family and for the jury."
CNN asked Ubiñas if she was surprised by Petit's stoicism in court.
"I think that's the one thing that many of us have been asking. We've been in awe of not just Dr. Petit, who of course has shown tremendous strength and grace through all this, but the whole Hawke and Petit families, I think, have shown the strength that many of us just wonder [if] we would have if we were put in that same situation."
Petit, asked after Tuesday's verdicts whether what happens to Hayes now matters to him, said that "what matters to me most is my family and my memories of my family."
"Over the last couple of weeks, I just kept trying to tell myself that good will overcome evil, and we'll keep trying to do good things and [I'll] try to refocus myself on the positive and stay away from the negative," he said.
In Session's Michael Christian and Swetha Iyengar and CNN's Brooke Baldwin and Jason Hanna contributed to this report.