The U.S. Secret Service, district attorney and postal inspectors showed ABC7 the evidence they found at Bradley Williams' apartment -- boxes filled with nearly 2,000 pieces of stolen mail, each victim's profile neatly organized alphabetically, and tools, computers and makeshift keys to open apartment building entrances and mailboxes.
Thirty-one-year-old Williams pleaded guilty Tuesday to identity theft and possession of stolen property. Two accomplices earlier pleaded guilty to lesser charges.
In all, more than 1,000 San Franciscans were victimized.
District Attorney Kamala Harris says this was a serious crime.
"The victimization lingers because it requires sometimes years for an individual to recover their identity and feel secure," she said.
Williams lived on Stanyan and Fell in the city's Panhandle District. Most of his victims lived within a half-mile of his apartment.
He snatched letters and parcels from people's mailboxes and altered the checks he found. He also used his keys to open mailboxes in apartment buildings.
Williams was finally caught in a surveillance operation.
Postal authorities say they are working on more secure mailbox keys.
"Better material, stronger metals, better box designs that are resistant to prying and tampering," James Rickher with the U.S. Postal Service. "Better lock design where the locks are resistant to bump keys or counterfeit key-making."
Williams was sentenced Tuesday to four years in prison.
His attorney objected to an ABC7 camera in the courtroom, saying his client did not want his identity known to the public -- an irony since he stole the identities of so many others.