"It's very easy to use, which is a very good thing," Palmer said.
With the man lying unconscious on the ground, a gym member called 911 while Palmer and an off-duty nurse began CPR.
"It's a lot going on, but you are just trying to do the best you can in the situation because it's literally life or death," Palmer said.
Next, they had to cut the man's shirt off and attach adhesives, and Palmer said he was nervous as he and the nurse kept at the rescue attempt until police and firefighters responded minutes later.
"They already delivered one shock, which is a good sign," Wilmington police Sgt. Chris Ahern said.
Ahern said Palmer's quick action helped save the man's life.
"That's almost like something you would get in a hospital," Ahern said. "He was still unconscious when he was up here. He started to breathe just moments before the (emergency medical technicians) got him on the stretcher."
Palmer credits his quick action to training he was given two months ago. Because of it, within 10 minutes, the man was breathing and talking outside in the ambulance.