He used the methods on more than Jews. Many more.

In his way of thinking, it was cheaper and cleaner.

I don't have a link. But the best I remember there were several reasons involved. One was to save ammunition for the troops. One was that it could easily be administered in a way that didn't raise suspicions until it was too late to escape. It was easy enough to herd them into showers with the pretense of delousing them, and then gas them once they were all locked in.

Because bullets were too expenive...He started off shooting those in the death camps but changed to gas as it did the job with less cost. By the way there were only 6 million Jews killed and 7 millon non-Jews killed.

He used many other methods like stated previously. Gas chambers were a very efficient way to kill them. It was cheap and fast. Ammunition costed money, and he wasn't going to waste a cent on such minorities.

because he thought it was a slow and horriable way to die. therfore he did it

Like many people have already said it was cheapest and they could exterminate many at a time. The link below explains it pretty well. Very disturbing when you read about how the made the victims believe they were going for "showers" and "sauna's". Then if you can believe it they then removed any teeth from the dead that had gold fillings with pliers....... http://en.wikipedia.org/wiki/The_Holocaust#Gas_chambers

I hope old HItler is burning in HEll

The problem was that even the killers who were shooting day after day thousands of people became mentally sick. Quite a few were committing suicide and most of them were drunk all day. So the gas chamber was more anonymous and the killer were not that much stressed.

Cost was an issue, but not the only concern (or even the major one). the real concerns were efficiency and personnel. Shooting people is very inefficient(a few at a time, and it often takes several shots to kill someone) and it is difficult to manage. People would sometimes run away, hide, fight back, etc. when they saw others being shot. So, the Nazi's needed a more "industrial" approach. They had started experimenting with gas (carbon monoxide from vehicle exhaust) to kill mental patients in Germany during the 1930s. THe first concentration camp chambers worked on this technology, but it was rapidly supplanted by cyanide gas (carbon monoxide was slow and fuel was expensive & in short supply). Another problem with shooting people is that they had to find people to do the shooting. This was not easy. During the early months of he occupation of Poland and soviet territories, there were serious problems finding enough Germans who would execute Jews (or civilians in general), and serious problems maintaining morale among those who would do it. "Industrialization" of the murder process was a solution to these problems as well. For an absolutely chilling account of the thinking of some of the people involved, read the autobiography of Rudolf Hoess, the first commandant of Auschwitz. Its titled "Kommandant in Auschwitz; autobiographische Aufzeichnungen " in German and was republished more recently in English as "Death Dealer: the Memoirs of the SS Kommandant at Auschwitz."

it was cost effective and less messy...