On Sunday evening, a lone gunman in Las Vegas left at least 50 dead and more than 400 injured at an outdoor music festival. Police said the shooter, identified as 64-year-old Stephen Paddock, killed himself as they closed in on him inside the Mandalay Bay Hotel.

The massacre is the deadliest in United States history, and for at least one major law enforcement official, it’s something Americans will just have to get used to.

During an appearance on MSNBC Live with Stephanie Ruhle, former New York City and Los Angeles police commissioner Bill Bratton sounded a grim tone, telling Ruhle that there was little police could do.

Also Read: Stephen Paddock: What We Know About Las Vegas Mass Shooter

“Commissioner, I won’t accept that this is the new normal. What is this?” Ruhle asked.

“This is the new normal in America, unfortunately. The number of mass shootings, the pace of them has been increasing, and now we have the worst ever,” he responded, adding that the real thing that law enforcement found surprising was why there weren’t more such incidents.

“The sheer availability of incredible weaponry in this country, the number of people who are emotionally disturbed or have grievances, it is so easy to do,” he said. “The term the ‘new normal’ is something security and policing in America is focusing on.”

The commissioner’s solemn analysis will likely only fuel the outpouring of grief that has cascaded across the United States as Americans woke up to the news. On Twitter, other performers from the Route 91 festival were joined by President Trump, Hollywood and music stars and the public in tweeting out their grief and condolences at the loss of life.

At this time, police believe Paddock acted alone, but a woman and companion — 62-year-old Marilou Danley — has been identified as a “person of interest” in the case.

“We have discovered. He was utilizing some of her identification and we’ve had conversation with her and believe her — at this time — not to be involved,” Las Vegas Metropolitan Police Department Sheriff Joe Lombardo said during a press conference early Monday morning.