Why did prince siddhartha gautama leave the palace to live in the wilderness for 6 years?

When Siddhartha was a boy.. for the first time he saw a weak, unhealthy, elderly man and this word Siddhartha had never seen... He went out into the world to find the meaning of life.. He wanted to live like other people... During his 6 years he nearly starved to death, cut himself to death, until he found a tree. Under that tree he meditated until he reached Nirvana, which is the most peaceful state... And then he went back to tell people his 8 fold path and 4 noble truths