Full coverage: 50 Dead in Orlando Nightclub Shooting

Thousands of people have gathered in downtown Orlando, in the southeastern U.S. state of Florida, to remember the 49 people who were killed in Sunday night's shooting -- and to pray for those who were wounded. The attack was the worst mass shooting by a single gunman in recent U.S. history and the deadliest assault on American soil since 9/11. We go live to our correspondent Sean Callebs in Orlando for more.

Q1. Sean, US President Barack Obama says there is no clear evidence that an outside terrorist group was involved in the shooting? What have investigators discovered so far? 

Q2. How has the local government reacted to the incident? What security measures are they taking?