SAN FRANCISCO (KTVU) -- San Francisco police announced Wednesday that a department investigation into a series of robberies also netted a cache with dozens of high-powered weapons and explosives.
Police said the handguns, rifles and 22 assault weapons were uncovered when investigators served a search warrant at a home in South San Francisco last week.
In addition to 38 weapons that were seized, police said they also discovered about 5,000 rounds of ammunition as well as explosives, including homemade dynamite and a pipe bomb.
"This is as large a seizure as I can remember, going back to 2009," said San Francisco Police Chief Greg Suhr.
Suhr said the investigation began a couple of months ago after serial robbers hit a gas station in the city's Bayview district on April 22. They then robbed three other businesses across the city within a few weeks.
The crimes were dubbed the "Letterman Robberies" because one of the suspects wore a letterman-type jacket in several of the cases.
56-year-old Homer Matthews was arrested near La Salle and Third streets on May 24 after officers recognized him from a crime bulletin, according to police.
Then last week, with the help of the San Mateo County Regional SWAT team, investigators searched a home in South San Francisco and arrested 31-year-old Austen Chin, who was described as the getaway driver.
The bomb squad was called during that investigation after police found explosives, including homemade dynamite and a pipe bomb.
"The mere fact that he was manufacturing or potentially manufacturing inside the home could have had devastating consequences to the neighborhood," said Lt. Bill Braconi of the SFPD's Bayview Station.
Police said their investigation revealed the guns had been offered for sale in the Bayview community.
"The question comes up reguarly - where do these weapons come from? I think this may be a potential source for the weapons that we find in the Bayview," said Lt. Braconi.
Braconi said they're still looking into exactly where the weapons came from and are enlisting the help of the ATF to try to trace them. As for the explosives, Braconi said they don't yet know what they were meant for, but there does not appear to be a link to terrorism.