Police across Southern California -- already on heightened alert following the Paris terrorist attacks -- were closely monitoring a mass shooting today at a San Bernardino treatment center for people with developmental disabilities.

COMPLETE COVERAGE: ACTIVE SHOOTER: Bomb Squad Now at Scene of Mass Shooting In California Los Angeles Police Department Officer Jenny Houser of the Media Relations office said the department had not been asked to assist authorities responding to the shooting that occurred around 11 a.m. at the Inland Regional Center, and the LAPD did not immediately mobilize in any way.

Details of the shooting were still sketchy and the motivations for the attack were not immediately known. Initial reports from the scene indicate as many as 20 people may have been shot at the center at 1365 S. Waterman Ave. There have also been unconfirmed reports of as many as 12 fatalities. Initial reports also indicated there may have been multiple gunmen, possibly wearing body armor and armed with automatic weapons.

Agents from the Los Angeles field office of the Bureau of Alcohol, Tobacco, Firearms and Explosives responded to the scene, according to the federal agency. Officials from the FBI were also dispatched to the scene. "We are confirming that we are responding to assist San Bernardino authorities who have the lead on the investigation," according to Laura Eimiller of the FBI.

News reports out of Washington, D.C., indicated that President Barack Obama has been briefed on the shooting. Gov. Jerry Brown was also briefed and "is closely monitoring this disturbing and ongoing situation unfolding in San Bernardino," according to the governor's Twitter page.

According to the facility's Facebook page, the Inland Regional Center has nearly 670 staff members and provides services to more than 30,200 people with developmental disabilities and their families in San Bernardino and Riverside counties.

"As an agency among agencies, Inland Regional Center coordinates with generic services to normalize the lives of people with developmental disabilities and their families by working to include them in the everyday routines and life rhythms of the community and by facilitating needed supports for them," according to the center's Facebook page. As the shooting investigation unfolded, the Los Angeles County Sheriff's Department issued a reminder that people can take steps to try to protect themselves in an active-shooter situation. The department has a website and video available with tips at activeshooter.lasd.org.