Authorities described how Syed Rizwan Farook and his wife, Tashfeen Malik entered the Inland Regional Center on Wednesday Morning wearing black tactical gear and carrying hundreds of rounds of ammunition.

Police said they entered the area where the staff party was going on and “sprayed the room with bullets,” firing 65 to 75 rounds during an attack that authorities described as a carefully planned “mission.”

Farook, 28, and Malik, 27, had more than 1,600 rounds of additional ammunition in the SUV they arrived in and another 3,000 rounds, 12 pipe bombs and bomb-making materials at their house in nearby Redlands, Calif., police said.

The FBI are treating it as an act of terrorism.