Years ago, the Burglar was the cellmate of the infamous depression era gangster "Dutch" Mallone, now an old man. In the 1930's, Mallone lived in New York City's Forest Hills section in the very same house that, at the time, was housing Peter's uncle Ben Parker and his wife, aunt May Parker.
It was long rumored that Mallone had a lot of money hidden away somewhere in his old house in Forest Hills. (it was revealed that the money was hidden in a box behind a wall inside the home, but had long ago been devoured by silverfish.)
Killing Uncle Ben
After robbing the studio where Peter Parker was doing performances as Spider-Man, the burglar was running to get away and Peter dressed as Spider-Man, allowed the burglar to get past him, thinking that it wasn't his problem and he was done being told what to do.
Weeks later, while Peter was making an appearance as Spider-Man, the burglar broke into the home of Peter's aunt May and uncle Ben, hoping to find Mallone's money. Making a threat towards aunt May, uncle Ben charged at the burglar and was soon shot dead by the man.
Upset his uncle Ben was dead, Peter went after the burglar, only to find out it was the same burglar that he could have stopped in the studio. After seeing his grave mistake, he left the man for the police, vowing no one to get hurt again and being the hero, Spider-Man.
Making another attempt at finding the money in ASM #200, aunt May was held captive by him in order to help him find it. Spider-Man showed up and took him down, only for the man to have a heart attack and die, due to the sheer terror and fear he had for Spider-Man.