I read somewhere, that at a certain part of the hike, the friend wanted to do an easier way, and Aaron wanted to do a harder way. So they separated and kept on calling each other's name to stay in touch. After a few minutes his friend didn't hear Aaron respond anymore.
I was at the Yom Tefilah in BMG today. Thousands showed up. There were tears flowing from the crowd - literally. The room was shaking. Never seen anything like that.