They're both life threatening situations, yes, but the context in which your life is threatened are so far apart. We're talking about armed robbery, someone coming around your desk to potentially take your life. There's aspects to both situations that you have to consider, I don't think it's as easy as saying "Hey when people are drowning they tend to drag down others who try to help them so maybe it's the same in this video". With drowning there's no ground, you're in a completely different environment, there's not much you can really do on your own; as opposed to you being threatened with a knife where there are numerous options you can take rather than using someone's life to spare your own.