Killing Yeast?

How do you kill yeast?? I ask because my beer came out with a strong matchstick/sulfer smell and taste and I'm under the assumption the it is caused by dead yeast? So I'm wondering what I could have done to kill my yeast and make them give me this?

Taken from
http://www.homebrewzone.com/off-flavors.htm
http://www.homebrewzone.com/sulfur.htm

Description: Flavor or aroma that resembles rotten eggs or sulfur.

Cause: Yeast autolysis (yeast cannibalism), bacterial infection.

Remedy: Do not let you homebrew sit on the primary yeast cake for a long period of time. Rack out of the primary when fermentation subsides, but be sure not to separate the wort off the primary yeast cake too soon also. Good sanitation also will reduce your chances of this off-flavor!

As suggested in the other thread you started about your Hefe having a sulfur smell after a few weeks, some yeast are known to produce sulfur smells - the yeast aren't the problem but the solution - give the yeast time to work and it will get rid of the sulfur smell.

Yeast can put off sulfur when fermenting. I wouldn't count it as autolysis unless its been on the cake for 2+ months, or its spent a majority of time over 80F

Yep only 3 weeK in the primary so I don't think that's the issue but it may just be what this yeast gives off. I just was under the assumption that yeast only go dormant not dead. So I was more or less interested in how yeast can die.

The last stage of the yeast life cycle is autolysis. This is when the cell dies and splits open. The flavors most associated with autolysis are kind of a salty/meaty flavor. If you can get your hands on vegimite, that is what autolysis would taste like, since vegimite is autolysed yeast.