CHICAGO -- Lance Armstrong said he finally cracked after he saw his son defending him against allegations from anti-doping authorities.
Anti-doping authorities and disillusioned fans might have wanted a different explanation - perhaps while expressing deep remorse or regrets, though there was plenty of that in Friday night's second part of Armstrong's interview with Oprah Winfrey.
Armstrong didn't break over the $75 million in lost sponsorship deals, or after being forced to walk away from the Livestrong cancer charity he founded and called his "sixth child." He didn't crack after his lifetime ban from competition.
It was another bit of collateral damage that Armstrong said he wasn't prepared to deal with.
"I saw my son defending me and saying, `That's not true. What you're saying about my dad is not true,"' Armstrong recalled.
"That's when I knew I had to tell him."
Armstrong was near tears at that point, referring to 13-year-old Luke, the oldest of his five children. It came just past the midpoint of an hourlong broadcast, a day after the disgraced cycling champion admitted using performance-enhancing drugs when he won seven straight Tour de France titles.
Critics said he hadn't been contrite enough in the first half of the interview, taped Monday, but Armstrong seemed to lose his composure when Winfrey zeroed in on the emotional drama involving his personal life.
"What did you say?" Winfrey asked.
"I said, `Listen, there's been a lot of questions about your dad. My career. Whether I doped or did not dope. I've always denied that and I've always been ruthless and defiant about that. You guys have seen that. That's probably why you trusted me on it.' Which makes it even sicker," Armstrong said.
"And uh, I told Luke, I said," and here Armstrong paused for a long time to collect himself, "I said, `Don't defend me anymore. Don't."'