A farmer in Oklahoma was killed by two water buffaloes he had purchased at a livestock auction the day before, police said.

"His farm was his dream, and I had the privilege of helping him with it for a little while," girlfriend Jennifer Green said in a statement.

The farm where Bradley McMichael, 47, died has been in his family for three generations. His fiancée described him as an experienced farmer who had worked with livestock since his teenage years.