I am, to say the least, completely agast at the number of DMs here who would kill off an absent player's character! In 25 years of gaming I have never been in a gaming group where this would be tolerated, or even contemplated! I know that if such a thing happened to my character that would be the last time I played with that group. Gaming is, after all, supposed to be fun. That does not sound like fun in the least.
In my current campaign we have some specific rules on attendance and your character. First off, we only game from October to the end of May. The rest of the year is too busy. That being the case, we set up a schedule well in advance, so that all gaming sessions are known and can be scheduled. We only play every other week. This is due to various players wanting to spend time with their children, an activity I hartily encourage. This generally means that attendance is quite high at our games.
If you are not able to to attend a game it is not the end of the world. The player can, if they choose, have their character perform backup duties, generally being "off screen" but with the party. Nothing bad will happen to their character during this time. They can give me acopy of their character and I will run it with the assistance of either another player, or our observer (wife of a player who comes over for the company and the food). Even then, I will not allow the character to die if the player is not there.
If the player decides to not have their character run by someone else, I give them the option of a "make-up" session. This has happened three times so far. For one character, it happened when the party encountered a major magical storm. The character was swept off by the storm, experiencing some very "Alice in Wonderland" encounters, and learned some things about himself and about the grand quest they were starting. His encounters were such that he got the same amount of experience each of the players got that game session. The other two times they players experienced a "dreamlands" encounter, learning about themselves and thier quest, and again earning the experience of those who were there.
I am completely shocked that a Dm would even contemplate killing an absent player's character. Imagine how you would feel if, due to family or work reasons, you could not make it to a game session, only to discover that your character died while you were gone. If it were me I would not only be upset, I would demand an explanation.