"We don't know exactly what happened because Dad was on his own at the time," said Raymond, who also works at a local engineering firm.
"Trevor saw that the cattle had escaped from the yard.
"He went to stop them from getting onto the road and that's when he found my father.
"He immediately started to administer CPR and he shouted to my mother to call an ambulance. He worked with dad until the paramedics arrived.
"They were absolutely brilliant. They were here in nine minutes.
"They did everything they could to revive him, but it was just too late."
Choking back tears, Raymond recalled how he dropped everything and rushed to his parents' home after he received a phone call alerting him to the accident.
"My mother told me to come quick because a bull had attacked Dad," he said.
"The factory is only a mile-and-a-half away from the home farm and I raced out the road.
"When I got there the paramedics were coming to the end of their procedure.
"I was there just for them to pronounce him dead. It was around 3.15pm."
Paying tribute to his "fantastic" father as "a quiet, unassuming man" with "a wealth of knowledge and experience", Raymond said his mother, brother and sisters Linda (47) and Avril (45) were struggling with their loss.
"Mum is numbed; it'll just take time to move on," he said.
"Time leaves things a lot easier to comprehend."
Describing farming as a vocation that's "in the blood", Raymond said his wife Valerie (46), an accountant, his son Glenn (17), and daughters Alex (23) and Kyra (19) all helped out on the farms when needed.
But he added that these days the younger generation must seek additional employment outside of the industry which has meant older people, like his father, were being left to carry most of the burden themselves.
"As life has moved on and times have become more difficult in farming, older farmers have been left to do the things round the farmyard and they're very much on their own now," he said.
"Their reactions aren't the same as what they were when they were younger, so I'd like to tell older farmers in particular not to take any chances and to ensure that they're not on their own."
Raymond said his father had died on the farm that "was gifted to him by his father Robert John in 1966 when he got married.
"Daddy was a wonderful man. He was a private man. He didn't go out," he added.
"His whole life centered around home."
The funeral will take place today at 1pm at Gillygooley Presbyterian Church followed by interment in Dublin Road Cemetery.
Rev Robert Herron, the Minister of Trinity and Gillygooley Presbyterian Churches, who knew Mr McKinley for more than 20 years, said the pensioner had just recovered from a serious illness.
"Alex was a hardworking man who simply loved the outdoors and working on the farm," he said. "For this to happen now is simply terrible."
The Health and Safety Executive said it was investigating the fatality. Figures from the HSENI reveal that there has been one death per year as a result of farm accidents involving bulls since 2014.
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