According to Borah,what is important about the fact that Chris cries when he says good-bye?

From the text:

When McCandless hugged Borah good-bye, she says, “I noticed he was crying. That frightened me. He wasn’t planning on being gone all that long; I figured he wouldn’t have been crying unless he intended to take some big risks and knew he might not be coming back. That’s when I started having a bad feeling that we wouldn’t never see Alex again.”