Don Derfler, from Portland, said he was waiting on a large delivery of mail and was happy to see the postman on his round.
But what he saw next was the last thing he expected.
Speaking to KATU TV, he said: ‘He was acting quite strange, so I thought I would watch him.
‘When he started pulling his pants down and defecating, I grabbed my camera and started taking pictures.’
He even took pictures of what was left behind.