SAN FRANCISCO (CBS SF) — Two men suspected in a series of San Francisco robberies are under arrest and a raid on one of the men’s South San Francisco home has turned up dozens of weapons and explosives.

56-year-old San Francisco resident Homer Mathews and 31-year-old South San Francisco resident Austen Chin were arrested last month, accused in a string of armed robberies of gas station and stores in San Francisco.

Police dubbed them the “Letterman Robberies” because one of them wore a letterman-style jacket during the heists.

Last week, police searched Chin’s South City home on Nursery Way and found 22 assault rifles and a .50 caliber revolver among 38 weapons total. San Francisco announced the results of the raid at a press conference Wednesday.

Weapons on display found during a raid on a home in South San Francisco.

Weapons on display found during a raid on a home in South San Francisco.

In addition, during the raid police found materials to make explosives as well as two crudely-made pipe bombs. “At that point we stopped our search and we contacted the San Francisco Bomb Squad who responded to the scene,” said San Francisco Police Sgt. William Braconi.

Investigators say there is no indication that terrorism was a motive.

“The fact that a cache like this exists is unnerving,” said San Francisco Police Chief Greg Suhr. “But the fact that now these weapons and these explosives are in the possession of law enforcement as opposed to somebody else, is the way we want it to be.”

Mathews and Chin are facing charges related to the robberies but not the weapons. That’s because they are trying to figure out if the San Mateo district attorney will take the case or whether it will be referred to the Bureau of Alcohol, Tobacco, Firearms and Explosives.