The excerpt does not show that his father and him were safe. Difficulties could have been waiting for them right after leaving the train. Moreover, there is no blame attached to Meir Katz for remaining on the train. He was just a victim of horrific circumstances. There was also no purpose in leaving him behind according to this passage. However, the passage does prove that very few people survived the train ride (in this case, 12/100).
It's life because when you are with someone you love and cherish you want to be around them all the time. And when you are together all you can wish to see is their smile and that makes your LIFE better.