The attackers who killed 14 at a California office party Wednesday before leaving behind a remote-controlled bomb and fleeing had ingredients for three more remote-controlled bombs waiting at their home bomb factory, but died in a hail of police bullets before they could use them, three sources tell NBC News.
After Syed Farook and Tashfeen Malik opened fire at San Bernardino's Inland Regional Center, they drove away in a black SUV. Police who arrived at the crime scene four minutes later found the suspects had left behind a remote-controlled device built from three pipe bombs and parts of a model car, among other components.
Authorities believe the suspects intended to detonate the device when law enforcement and emergency personnel responded to the shooting, but the device never exploded.
The couple drove back to their apartment in Redlands, which was already under surveillance as they approached. They were killed in a firefight with police. A search of their car revealed a remote controller that the suspects may have intended to use to detonate the device at the office party.
Inside the couple's residence, authorities found enough material to construct three more similar devices, including more model cars and a dozen pipe bombs in a bag. Authorities believe the material could be evidence that the couple planned additional attacks after the Inland Regional Center shooting.
The components found also included straight and elbow pipes, internal plugs and caps for the pipes, tape, wiring, wire strippers and cutters, a soldering gun and an electric drill. There was also at least one container of smokeless powder and a number of miniature Christmas tree lights with green insulated wire.
Christmas tree bulbs were used by the Tsarnaev brothers for the ignition systems in the explosive devices they used during the 2013 Boston Marathon bombing. The on-line al Qaeda magazine "Inspire" recommended the bulbs as bomb components in advice about making home explosives.