The patient had been been experiencing chest discomfort and pain, which became more intense and woke him from his sleep on the night of the call.
In 10 minutes, he was being assessed by Mr Fuller, and went into cardiac arrest 15 minutes later.
Two ambulances, and ambulance officer vehicle attended, with Mr McWilliams taken for treatment at Essex Cardiothoracic Centre at Basildon Hospital.
Mr Fuller said he was “so grateful” he was able to be there when Mr McWilliams went into cardiac arrest and use his training.
“It’s quite emotional and a great feeling knowing that you have saved someone’s life,” he added.
“I was a community first responder before I joined the ambulance service, and I love every minute of working and volunteering for my community.”
Claire Ruddy, who manages community response in Essex, said the service was under “significant pressure” at the time, and Mr McWilliams may not have had the intervention in time had Mr Fuller not attended.