As per my signature.... for years veggie and years vegan...
And as for why, well there are a number of reasons, but the trigger was a biology experiment at school when I was 11 or 12. The actual experiment wasn't the problem, it was what happened afterwards that I didn't handle very well as an 11 year old and neither did the other girl involved.
We had an experiment where we had to dissect an egg at various stages of its growth whilst being incubated. We had 2 lessons a week and in each lesson we would dissect another egg, kill the chick with ethanol (?) and then chart its development. We didn't dissect the embryo just look at it. The remaining eggs in the incubator then hatched and we watched their development and growth daily for about a week, On the Friday, there was "The School Dance" competition. It was expected that everyone took part, but there were some like myself and another girl who were just not interested (It was an all girls school btw). So we had to go to lesson as normal. So what do you do with 2 girls on a Friday afternoon for a biology lesson? Nothing. We had to entertain ourselves. We did all our homework and then played with the chicks which were at the really cuddly and cute stage... On the Monday morning we came back into school and at the first break we both went over to the lab to see them only to find they had been killed and fed to the biology teachers' dogs over the weekend. Now, at my current age, I could handle that and accept it and I have no issues personally killing (by hand if necessary) an injured animal and have been known to do so (at the scene of an accident where someone had it a deer - he was a big macho guy, went over into the woods (moving the injured deer off the road) and found when faced with reality he could not kill it, me the women on the scene was left to kill the injured deer which was beyond help and clearly going to die a painful and lingering death id not put down). Then as a pre-teenage girl it was too much, both of us were vegetarian before the end of that term and both of us stayed vegetarian throughout our entire time at the school (7 years).
I'm not one of those every animal vegan extremists. I have no issues in people eating road kill if they want to and I have no issues in people shooting rabbits - the rabbit population is not a cute and cuddle thing, it is a pest and they are a menace. I have seen and experienced first hand the damage rabbits do when their numbers get out of control. I don't agree with a lot of the farming methods, but I don't wish to go into it here.