Mark Kelly, a former astronaut, and his wife have spent years speaking for gun control since Ms Giffords survived a 2011 assassination attempt which resulted in a bullet to the head while speaking in her Arizona Congressional district.
The comment was made in front of Capitol Hill in Washington and Mr Kelly said he and his wife had been trying to get Congress “to summon the courage” to vote against the powerful lobby of the National Rifle Association (NRA).
In the 2016 election cycle, the NRA spent over $1m in contributions to candidates, about $3.6m in lobbying efforts, and a whopping $54.4m in “outside spending” that went to political action committees, according to Open Secrets.
Mr Kelly highlighted other mass shootings such as the Aurora, Colorado movie theatre shooting in 2012, the heinous murder of 26 children and teachers in Newtown, Connecticut in 2014, and the previously-deadliest shooting in US history - when 49 people were killed and 58 injured in an Orlando nightclub.
“Despite senseless, deadly gun-related domestic violence...the response from Congress has been to do nothing. Absolutely nothing,” Mr Kelly said emphatically.
“Your thoughts and prayers aren’t going to stop the next shooting. Only action and leadership will do that.”
Mr Kelly blasted Donald Trump and Vice President Mike Pence for offering hollow tweets and statements, saying “Americans need more than our president’s prayers. We need his plans [on gun law reform].”
In the hours after the Las Vegas massacre, the White House Press Secretary Sarah Huckabee Sanders said that it would be “premature” to discuss gun control policy.
She said “there’s a time and place for a political debate” but in the wake of deadliest mass shooting in modern US history was not it.
Mr Kelly responded by asking: “how many times can we say that over and over again, ‘Now is not the time?’ Well, today is the time.”
Both he and Ms Giffords are gun owners, but Mr Kelly said “we can respect the Second Amendment and the rights of responsible gun owners, and at the same time, we can keep guns out of the hands of criminals, domestic abusers, potential mass shooters, and idiots.”
Ms Giffords urged her former colleagues to take action as well: “The nation is counting on you.”
A crowd of 21,000 people gathered for the Route 91 Harvest Festival on the Las Vegas strip to listen to country music star Jason Aldean on Sunday night.
Stephen Paddock, the alleged gunman, shot several hundred bullets from the 32nd floor window of his room at the adjacent Mandalay Bay Hotel and Casino.
Police believe Paddock shot himself just before they stormed the room, where 23 guns and several rounds of ammunition were found among his possessions.
He lived in a retirement community in Mesquite, Nevada, about 80 miles northeast of Las Vegas were police found an additional 19 weapons.
His brother Eric said the family had no knowledge of any mental problems, religious, or political affiliation Mr Paddock may have had.
He described the suspected gunmen as multimillionaire real estate professional who liked to gamble and "was just a guy...he snapped or something."
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