Radley says he dropped the phone as soon as he saw Rodger's face.
"I was just like, 'Wow, this guy lived literally three doors down from me,' " Radley told The Salt Lake Tribune by phone Monday from California, where the senior running back on the University of Utah football team is visiting home. "He was really quiet. He never said anything."
Media outlets have since published the killer's 141-page life story, which includes grievances against myriad unwitting people Rodger perceived as enemies, many accused for being women or being liked by women.
The latter group apparently includes Radley.
At no point does Rodger write that Radley treated him poorly.
In fact, he writes that Radley was "very nice at the time" when they played together as elementary school students in Woodland Hills, Calif. His reason for hating Radley was that he was "immediately popular with the pretty girls of his grade" when they attended the same middle school.
"Literally, I've done nothing wrong to him whatsoever," Radley says. "I really hung out with him in fourth grade. After that, he was kind of doing his thing. I was into sports and he was kind of into other things."
Radley remembers Rodger vividly, down to his black Blink 182 hoodie with a rabbit logo on the front. They sat at the same table in their fourth-grade classroom, and they're in the same class picture.
Rodger's stepmother was worried about her son's reluctance to socialize, Radley remembers, so she frequently asked Radley to hang out with him.
"I would always play outside and try to catch lizards and stuff like that, and his mom would try to engage us and say, 'Oh, come over! We have lizards in our backyard!' or 'Come over, we have pizza!'"
The boys would play video games, and when Radley reacted to something that had happened, Rodger would just smile.
"He was overly quiet," Radley says. "Unusually quiet."
They lost touch during middle school, and Radley hadn't seen him since nor did he remotely imagine that Rodger bore him ill will.
He hasn't yet read Rodger's so-called "manifesto," but his girlfriend is about halfway through it and has been relaying details.
"You hear about this in horror movies and stuff like that," Radley says. "I would never imagine this would happen for me to know someone who it happened to, it's disturbing."
But allowing this to affect him too much is selfish, he says it would hurt his schoolwork (he's working toward a master's degree in sociology) and it would let down his teammates at the U.
He simply hopes people will come to better understand the types of problems that affected his childhood playmate, and work to prevent such tragedies in the future.
"I feel like this could have been avoided if people just talked to him."
The Associated Press contributed to this report.