Authorities were told 'to be aware of possible followup'

By Susan Keating Greg Hanlon
December 04, 2015 02:00 PM
Johnny Dodd

A Southern California police source tells PEOPLE that local police are on high alert for additional attacks following Wednesday’s mass shooting in San Bernardino that killed 14 and injured 21.

“We are being extremely vigilant for additional attacks,” the source says.

The source says that the “lead agency” in the investigation – which the source did not specify – alerted local police “to be aware of possible followup.”

The source adds, “The signs [of Wednesday’s massacre] point to terror. What kind, we don’t know. Was it a one-off deal? Part of a larger action? We don’t know. We have been told to proceed with extreme vigilance.”

A different source connected to the investigation tells PEOPLE that authorities the guns used in the attack by the shooters – husband and wife Syed Rizwan Farook, 28, and Tashfeen Malik, 27 – seemed to have been carefully coordinated by the attackers.

“This points to a level of training and education,” says the source. “There was a measure of sophistication in how they chose their weapons. That knowledge alone is quite valuable to us.”