He was at one site where he had to climb on top of a tank to read a gauge. He had just climbed to the top and was about the read the gauge when he clearly heard someone call out his name, "Mike!" Thinking it was odd because he thought he was completely alone and hadn't heard another truck pull up, he shouted back, "Up here!" There was no response. Again he turned to read the gauge when he heard it again, "Mike!" He decided to climb down and see who was looking for him.