ATF: San Bernardino shooters used four guns, explosive device

02:06

The suspects in the mass shooting at a San Bernardino holiday party, Syed Rizwan Farook, 28, and his wife Tashfeen Malik, 27, were armed with four guns, an explosive device, and several magazines of ammunition in a "well-planned" attack, police and federal officials say. NBC’s Pete Williams reports for TODAY.