Three people wearing ski masks and armed with at least one gun stole gold nuggets from San Francisco's Wells Fargo History Museum Tuesday morning after they rammed an SUV into the building's entrance.

Police said that at least 10 ounces of gold were stolen, valued at about $10,000.

The robbery took place at about 2:30 a.m. at 420 Montgomery St., where the glass front of the building was left shattered and swarms of police officers were surveying what happened and what was stolen, a police investigator told NBC Bay Area.

A dark Chevy Suburban was towed away just before 7 a.m. Officer Grace Gatpandan said that the three suspects had ditched the SUV, their faces covered, and held the security guard at gunpoint before taking the gold nuggets from a display case.

The trio took off in a second vehicle, described as a four-door sedan. Gatpandan said she does not know if this getaway car was waiting for them with another driver inside or if it was strategically parked somewhere. She said the Chevy was stolen from San Bruno.

Kevin Woodsford, who was on the scene afterwards to replace the glass, has been inside the building before. He noted that the museum has lots of "valuable stuff and antiques you probably can't replace."

"It's pretty crazy," he said. "It's a bold job to pull off."

The museum honors Henry Wells and William Fargo, who founded their financial services company in 1852. The museu's website prominently advertises gold nuggets as one of its featured attractions.

In a statement, Ruben Pulido, a Wells Fargo spokesman said: "We’re disturbed this happened to the Wells Fargo History Museum, but are grateful no team member was harmed. Additionally, the historic stagecoaches on site were not damaged." He vowed the museum would soon reopen.

Police said they have made no arrests but did not there have been several smash-and-grabs recently in the city.

In November, burglars drove a car into the Chanel store off Union Square. Two weeks ago, two men backed a U-Haul van into the Patagonia store near Fisherman’s Wharf.

“It does not appear that these were related,” San Francisco police spokeswoman Officer Grace Gatpandan said.

NBC Bay Area's Mark Matthews contributed to this report.