The Origin of Spiderman:
 

Bitten by a radioactive spider, a ordinary teenager, Peter Parker, was given unspeakable powers. At first, Peter used his new found powers to earn some quick money as a wrestler. One night while at the arena, a burgler ran past Peter. The security guard yelled at Peter to stop him, but Peter did not. This one act changed Peter's life forever. Peter came home that night to find that his Uncle Ben was killed by a burgler. Peter donned his spider costume one more time to find his Uncle's killer. He overheard from a police officer that he was hold up in a warehouse. When Peter confronted his Uncle's killer, Peter realized that the killer was the burgler from the wrestling arena. To honor his Uncle's memory, Peter Parker became "The Amazing Spider-Man". Peter learned that with great power comes great responsiblity.

(information copied from here)