- Trump not ruling out eliminating fiancée visas following San Bernardino massacre
- Trump believes the killers' families were aware of the plans to murder
"We're going to have to start looking at people very closely because we can't allow this to happen to our country," Trump said. "I'm not ruling out anything. I don't rule out anything. If people come in and blow up people and shoot people and kill people, I don't rule out anything."
Authorities say Syed Rizwan Farook, a U.S. citizen, and his wife, Tashfeen Malik, a permanent resident, massacred 14 people at a holiday party Wednesday at the Inland Regional Center in San Bernardino, California.
They met face to face when Farook visited Saudi Arabia, where Malik had moved from her native Pakistan around the age of 18 or 20. She later came to the United States on a fiancée visa and became a legal permanent resident.
Trump said the government needs to better monitor the families of suspected terrorists. He said the shooters' families had to know Farook and Malik's plans.
"We have to start looking at families. We have to look at them tough," he said. "Generally speaking the wives know what's going on. I believe that the sister of the killer -- I watched her interview-- I think she knew what was going on."
"I think his mother knew what was going on. Anybody who went into that house or that apartment knew what was going on," he added. "We better get a lot tougher and little smarter or we're in trouble."
The Republican frontrunner addressed a range of topics related to the Southern California killings. The mogul mocked the San Bernardino killers for fleeing after killing 14 people at a center for people with developmental disabilities.
"They're chickens**t, so they left early, because they didn't want to get caught," he said.
Trump also doubled down on monitoring certain mosques in America, a proposal that has drawn criticism.
"We have to be vigilant. Now that includes with mosques and we better be smart."