"I mean, for the life of me, I don't know why the hell people have to have an assault weapon," said Panetta, who is visiting NATO allies in Europe before leaving the Defense Department.
The gun control issue came up during a question-and-answer session with members of the 173rd Airborne Brigade in Vicenza, Italy.
"I believe in the Second Amendment," he said. "I believe people have the right to own weapons. But, you know, when these kids are getting killed in schools -- and I know it's tragic. I know what an impact it must have on those families -- we just have to try to do what we can to make sure that we take some steps here to try to protect those kids."
Panetta, a former California congressman who served as President Bill Clinton's White House Chief of Staff in 1994 when a 10-year ban on the sale of assault weapons passed Congress, said the government can take actions to reduce gun violence that don't undermine gun ownership rights.
He said he also supports prohibitions on armor-piercing ammunition.
"I think there are -- you know, there are areas like armor-piercing bullets -- I mean who the hell needs armor-piercing bullets except you guys in battle?" he asked. Panetta said he has hunted ducks since age 10 and loved "to share that joy with my kids."
It's going to be a tough debate," he said. "This is not going to be easy."