The Note: A nation reels as mass shooting strikes Las Vegas

At least 50 people are dead and 200 are injured in a shooting in Las Vegas.

This weekend would suggest that there is little or nothing exempt from the politics of division, as practiced by President Trump. Now comes a fresh test – the worst mass shooting in U.S. history, not to mention the Trump presidency, at a country-music festival in Las Vegas overnight. The ensuing days will test the president's tone, and – depending on what's learned about the shooter and his motivations – is very likely to involve the president's name in some way. Can he resist the urge to punch – or counter-punch – in a time of national tragedy, compounded by an unfolding crisis in Puerto Rico? These types of stories always wind up being political, whether it's about gun control or the sources of the dark forces in a gunman's life. There's a numbing familiarity to it all. What's new to the equation is Trump, whose instincts have rarely taken him in the direction of unity. The president spent the weekend being defiantly Trump, even down to his golf-course routine. This week will challenge him to recognize what this moment calls for.

WHAT YOU NEED TO KNOW TODAY

  • At least 50 are dead, 200 injured in a shooting near the Las Vegas strip in what is now the deadliest mass shooting in U.S. history.
  • President Trump has been briefed on the tragedy in Vegas, according to the White House. "We are monitoring the situation closely and offer our full support to state and local officials. All of those affected are in our thoughts and prayers," an administration official said.
  • Trump tweeted: " My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you!" The first time we could see Trump respond on camera is 11 a.m E.T., when he leads a deregulation summit at the White House.
  • Tweeting from his Bedminster golf club, Trump slammed San Juan's mayor for "poor leadership" and said of local officials "they" want everything "done for them."
  • The U.S. Supreme Court begins its new term today. On the docket, gerrymandering and a Colorado baker's case to refuse to make a wedding cake for a gay couple. Notably off the docket: Trump's travel ban.
  • Trump undercuts his secretary of state: Trump said he told Rex Tillerson you're "wasting" your time negotiating with North Korea a day after Tillerson said the U.S. has open lines of communication with Pyongyang.
  • Facebook will hand over more than 3,000 Russia-linked ads to all three congressional committees investigating Russian election interference today, a Facebook official confirms.
  • President Trump has a series of meetings today: A group of Republican governors, the prime minister of Thailand today, and dinner with Republican congressional members tonight.
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    The Note is a daily ABC News feature that highlights the key political moments of the day ahead. Please check back tomorrow for the latest.