"I touched myself, and it was blood all over my hands. And my clothes," Cohn says on Friday's "20/20."
"And I realized I was the one who'd been hit ... every second that passed by, I thought, that's the last one. That's the last second I'll be here."
Cohn and several members of his band were leaving a show in Denver Aug. 7 when they were shot at by an alleged carjacker, who's since been charged with attempted murder.
Cohn, a Grammy winner ("Walking in Memphis"), was hit in the temple — and miraculously survived.
"Please don't let me die, I have children," Cohn says he was thinking after being shot. "I have a wife ... and it was terror, disbelief and just a prayer. Just please don't let this be it.
"'Cause I was aware, I mean, it almost seemed just like ... this wasn't supposed to be the end."
Cohn and Vargas are interviewed, along with band member Shane Fontaine and tour manager Tom Dube — who were with Cohn when he was shot — on Friday's "20/20" (10 p.m. EDT), along with the paramedics and doctors who treated Cohn.
"I could see a perfectly round hole in his head, which I knew had to be a bullet," Fontaine says. "He was looking to me for reassurance and he was speaking of his family, his wife and his children, and that he didn't want to die, you know?"
Dr. Jason Haukoos, who read Cohn's brain scan, says he's lucky to be alive.
"I suspect the bullet actually struck the skull, not with enough velocity to fracture it but enough to stop it and keep it in this location," he says.
"Had his head turned five degrees to the left, it could've easily gotten into his eye. It was that close."
Vargas, who rushed to Denver to be with Cohn, says it will take her husband time to recover from the terrifying ordeal.
"I think the thing I've learned about all of this is sensitivity to people who have experiences like this, going forward," she says.
"Long after the physical wounds are healed, I think my husband's going to really be struggling with the psychological effects of what happened.
"This is not something you just sort of go, oh, got carjacked and shot, all right, move one.
"You just don't move on."