"Because we have done nothing, the mass shootings continue. I know these are harsh words, but I believe it in my heart; I believe there's an unintentional endorsement that gets sent to these mass murders when slaughter after slaughter Congress does nothing," Murphy said from the Senate floor.

Murphy added that if the Senate doesn't act by changing gun control and background check policy "it starts to look and feel like complicity."

At least 59 people were killed and more than 520 people injured during a shooting at a country music festival in Las Vegas on Sunday night — marking the deadliest mass shooting in modern U.S. history.

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Murphy has become a prominent critic of the nation’s lack of gun control. His home state had a mass shooting in 2012 when 26 people were killed in a shooting at Newtown Elementary School.

Democrats are using the latest shooting to renew their push for new legislation. Murphy told reporters separately on Monday that he will introduce a background check bill.

But any push to crackdown on gun control or background checks faces an uphill fight in the GOP-controlled Congress. Senators rejected a background checks amendment last year days after a shooting at a Florida nightclub.

Murphy called mass shootings in the United States a "festering, lingering paradox" that the country is still suffering from.

"We have become normalized and regularized to 50 people losing their lives. This is a uniquely American problem, by the way," he said.