WASHINGTON — Sen. Bob Casey called for Congress to toughen gun laws in the aftermath of the Las Vegas shooting that killed more than 50 and injured hundreds in the worst mass shooting in U.S. history.

"While we pray for the victims of this horrific attack and their families, it is not sufficient to just offer thoughts and prayers," Casey, a Pennsylvania Democrat, said in a news release Monday, becoming one of the first lawmakers to call for new laws following the shooting.

"Congress must engage in a robust debate about common sense ways to keep guns, particularly military-style weapons, out of the wrong hands," Casey said. "Congress should take up and vote on legislation to ban military-style weapons, limit the size and capacity of magazines, which contribute to deadly mass shootings, and put in place universal background checks. If Congress continues to fail its most basic obligation to keep America safe, then these mass shootings will continue to occur."

Some other Democrats also joined Casey's call, though with a Republican-controlled Congress, the odds of any new gun law passing are close to zero.

Very little was publicly known about the shooter and his weapons by mid-day Monday, including whether he would have been stopped by a background check. Early questions have arisen, based on the audio of the shooting, over whether he had an automatic weapon. Such guns are already heavily regulated.

Proponents of tougher laws, however, have long pushed to ban semi-automatic weapons as well. Such guns have been used in numerous mass shootings, including the 2012 school massacre in Newtown, Conn., an incident that prompted Casey to change his views on gun laws and become an outspoken advocate of some new restrictions.