The shooter's mother, Nancy Lanza, owned legal guns and had gone shooting at a range with Adam Lanza, federal sources said.
Casey Butler said he also takes his kids to shooting ranges, but he believes their situation is different than what it might have been for the Lanzas.
"Me taking my 4-year-old or my 8-year-old out to shoot a gun, I know they're responsible enough to do that," he said. "I know their mental health."
If there is something wrong or questionable about a child's mental health, Casey Butler said, the last thing they need to be doing is learning how to shoot or be around guns.
"If I felt my daughter was crazy and I needed to take her to an institution, it would break my heart, it would be tough to do," he said. "But, at the same time, I would do it for her benefit. I would do it for my benefit. I would do it for everyone's benefit. I wouldn't take her out shooting guns."