Federal law generally requires firearms dealers to conduct background checks on gun buyers, and prohibits sales to convicted felons and some people who have been legally declared to have mental problems. State restrictions vary widely on weapons and waiting periods.

In Virginia, where Cho bought his guns, Attorney General Bob McDonnell said the disconnect between state and federal laws on background checks is something his lawyers are working to fix. He cautioned, though, against any federal response that would infringe upon individual rights.

Newt Gingrich, a former House speaker and potential Republican presidential candidate, suggested future tragedies could be halted if there were greater access for people to legally carry concealed weapons.

"There have been incidents of this kind of a killer who were stopped because, in fact, people who are law-abiding people, who are rational and people who are responsible, had the ability to stop them," Gingrich said.

Leahy spoke on CBS' "Face the Nation." Specter spoke on "Fox News Sunday." McDonnell spoke on CNN's "Late Edition." Gingrich appeared on ABC's "This Week."