"Take a look. I mean, you look at the names, you look at what’s happened. You tell me."
"I think it was terrorism,” he later added.
Police have not determined the motive in the killings -- which left 14 dead -- but have not ruled out terrorism. The suspects, Syed Farook and Tashfeen Malik, were killed in a gun battle with police.
Trump also said the rise of mass shootings in the United States is connected to mental health.
"It's mental health, and it's also really strength. We need strength. We have weak government," he said. "We need strength. And I have to tell you, I think the police out there did a fantastic job and law enforcement."
After the mass shooting in Paris last month, Trump said the incidents might be preventable if more people had guns.
“Nobody had guns but the bad guys," he said. "Nobody. Nobody had guns and they were just shooting them one by one and then they broke in and had a big shoot out and ultimately killed the terrorists and I’ll tell you what you can say what you want but if they had guns, if our people had guns, if they were allowed to carry it would have been a much much different situation.”