LAS VEGAS, NV - OCTOBER 01 People run from the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas,...
David Becker

The worst mass shooting in modern American history

— Updated

In the immediate aftermath of a mass shooting, it takes time for key details to come into focus, but at this point, we're starting to get a better sense of what transpired in Las Vegas overnight, in what appears to be the worst mass shooting in modern American history.

A lone gunman released a rapid-fire barrage of bullets from a 32nd-floor Las Vegas hotel room late Sunday, killing at least 50 people and injuring more than 400 others at an outdoor country music festival, police said. [...]

The shooter, who was identified by law enforcement officials as Stephen Craig Paddock, 64, of Mesquite, Nevada, fired shot after shot from the Mandalay Bay Resort and Casino down on the crowd of about 22,000, sending terrified concertgoers running for their lives.

According to the latest details reported by NBC News, the gunman began his attack shortly after 10 p.m. local time (1 a.m. ET), and though some of the early accounts suggested Paddock was killed in his hotel room by the police, the latest reports suggest the shooter had killed himself before his room was breached.

Las Vegas Metropolitan Police Sheriff Joseph Lombardo told reporters Paddock had more than ten rifles in his hotel room. Local officials have not described a possible motive for the mass murders.

The previous record for the deadliest shooting in the United States was set last year at the Pulse nightclub in Orlando, where a gunman killed 49 people before he was fatally shot during a standoff with police. The precise death toll in Las Vegas is not yet clear, but local law enforcement has put the total at "more than 50."

As for the response from policymakers, a familiar debate is underway.

The worst mass shooting in modern American history was met with immediate calls for action on gun control Monday from some Democratic lawmakers.

While most of their colleagues on both sides of the aisle stuck to sending condolences to victims and their families in the Las Vegas shooting, Connecticut's senators expressed outrage that Congress has not done more to restrict access to deadly firearms five years after the Sandy Hook Elementary School shooting in Newtown.

"Nowhere but America do horrific large-scale mass shootings happen with this degree of regularity," Sen. Chris Murphy, D-Conn., said in a statement.

"This must stop," Murphy continued. "It is positively infuriating that my colleagues in Congress are so afraid of the gun industry that they pretend there aren't public policy responses to this epidemic. There are, and the thoughts and prayers of politicians are cruelly hollow if they are paired with continued legislative indifference. It's time for Congress to get off its ass and do something."

According to reports published before the Las Vegas slayings, the House is expected to vote this week on repealing federal limits on gun silencers and a proposal to allow states to honor conceal-carry permits across state lines. Whether Republican leaders will delay consideration of the measures is not yet clear.