Volunteers help amid tragedy

Henry Liu, a Chinese tour guide, was driving his tour bus near the Las Vegas Strip as he headed back to his hotel after a day's work.

When he got closer to the Strip around 10:30 pm local time, he suddenly heard a burst of popping sounds.

"I thought it was fireworks at first, but then I realized it was the sound of gunshots," Liu said. "I saw police cars fly past with sirens blaring, and the police were all fully armed."