Vandals struck San Francisco's The GLBT History Museum on Monday morning.

Officials say vandals shattered two of the museum's large plate glass windows shortly before 5AM.

America's first-of-its-kind museum opened last year in the heart of the city's gay neighborhood, the Castro District.

Paul Boneberg, executive director of the GLBT Historical Society, the organization which runs the museum, expressed gratitude for the outpouring of support the group has received.

“That support speaks to the important role the museum plays in advancing understanding of GLBT history and culture,” said Boneberg in a statement.

Boneberg labeled the attack vandalism, saying that no theft occurred.

“It's clear that this was vandalism. We don't know who smashed the windows or why they did it.”

“When the alarm sounded at 4:50 this morning, the security firm immediately summoned the San Francisco Police Department and notified our staff, who were on the scene very quickly,” Boneberg explained. “In short order, the broken glass was removed and the windows were boarded over.”

Total cost of the damage is not yet known. Donations can be made at the museum's website.