“Probably we’ll find out with him, like we did with numerous of the others, that gee whiz, they were loners and they were probably sick. You know, oftentimes this happens and the neighborhood says, you know, we sort of saw that about him, and it really looked like he could be a problem.”

A gunman, who has been identified as Chris Harper Mercer, shot and killed nine people and wounded seven Thursday at Umpqua Community College in Roseburg, Oregon.

“But you know, it’s awfully hard to put somebody in [an] institution for the rest of their lives based on the fact that he [looks] like he could be a problem. It is a terrible situation. It’s huge mental illness,” he said. “You’re going to have these things happen, and it’s a horrible thing to behold. Horrible.”

Mr. Trump said that “for the next million years, you’re going to have difficulty.”

“People are going to slip through the cracks, and even if you did great mental health programs, people are going to slip through the cracks,” he said. “I’m sure it’s going to be found that this guy was probably, you know, they seem to be loners, they have all sorts of difficulties. … What are you going to do, institutionalize everybody?”