LAS VEGAS >> A gunman on the 32nd floor of a Las Vegas Strip casino opened fire on an outdoor music festival, killing at least 20 people — including two off-duty police officers — and wounding more than 100, officials said early Monday. Country music star Jason Aldean was performing on stage when the shots began ringing out Sunday night at the Route 91 Harvest Festival. Officers confronted the suspect on the 32nd floor of the Mandalay Bay Hotel and Casino across the street from the concert and he was killed, Clark County Sheriff Joseph Lombardo said. Authorities did not...