Reports of an active shooting situation at the Inland Regional Center were confirmed by law enforcement officials around 2:15 ET. The San Bernardino Police Department said up to three shooters were inside the large building complex, located at 1365 S. Waterman Avenue.
A police spokeswoman told reporters the suspects were heavily armed and possibly wearing body armor, the Los Angeles Times reported.
At least 20 victims have been reported down, but there might be more, according to the San Bernardino Fire Department.
Media sources are reporting this as a mass casualty event. Local news station ABC 7 cited a “very reliable” source confirming that 12 people were killed in the shooting spree.
The situation is still considered active as law enforcement officials search for the shooters.
The Inland Regional Center is a private, nonprofit agency that helps people with developmental disabilities. It has a staff of nearly 670 that provides services to more than 30,000 clients, according to its Facebook page.
The shooting in San Bernardino comes just days after another high-profile mass shooting at a Planned Parenthood clinic in Colorado Springs, Colorado. That incident left three people dead, including one police officer and two civilians. According to an analysis released in August, the United States has averaged more than one mass shooting for each day of 2015.