DescriptionLas Vegas Metropolitan Police Department Undersheriff Kevin C. McMahill joins "CBS This Morning" by phone to discuss the investigation into the deadly mass shooting at the Route 91 Harvest country music festival. Police believe the gunman, identified as 64-year-old Stephen Paddock, killed himself before police entered his room on the 32nd floor of the Mandalay Bay Resort and Casino, across the street from the concert. This is the deadliest mass shooting in U.S. history, with more than 50 people killed and 400 others injured.Subscribe to the "CBS This Morning" Channel HERE: http://bit.ly/1Q0v2hE Watch "CBS This Morning" HERE: http://bit.ly/1T88yAR Watch the latest installment of "Note to Self," only on "CBS This Morning," HERE: http://cbsn.ws/1Sh8XlB Follow "CBS This Morning" on Instagram HERE: http://bit.ly/1Q7NGnY Like "CBS This Morning" on Facebook HERE: http://on.fb.me/1LhtdvI Follow "CBS This Morning" on Twitter HERE: http://bit.ly/1Xj5W3p Follow "CBS This Morning" on Google+ HERE: http://bit.ly/1SIM4I8 Get the latest news and best in original reporting from CBS News delivered to your inbox. Subscribe to newsletters HERE: http://cbsn.ws/1RqHw7T Get your news on the go! Download CBS News mobile apps HERE: http://cbsn.ws/1Xb1WC8 Get new episodes of shows you love across devices the next day, stream local news live, and watch full seasons of CBS fan favorites anytime, anywhere with CBS All Access. Try it free! http://bit.ly/1OQA29B ---Delivered by Charlie Rose, Norah O’Donnell and Gayle King, "CBS This Morning" offers a thoughtful, substantive and insightful source of news and information to a daily audience of 3 million viewers. The Emmy Award-winning broadcast presents a mix of daily news, coverage of developing stories of national and global significance, and interviews with leading figures in politics, business and entertainment. Check local listings for "CBS This Morning" broadcast times.