Rescue dog saves his owner's life

[Catherine]

Dogs really are more aware of their surroundings than we are. Their senses are better than ours and they listen to them.
If Leo heard the rock slipping (or something that alerted him)  that would explain him knowing there was danger. He also acted on what he sensed. He trusted his instincts. His willingness to act is what saved the day.

We don't tend to sense things and we don't act on them. 
This is why dogs make good service animals. They are aware and they act responsibly.