Online gamers heard gunshots through their headphones. Hundreds of miles away, 2 people were dead

Across the world every day, millions of people play online video games with groups of friends or complete strangers, connected only by the internet and their headphones. Players compete against each other or in teams, in games such as "League of Legends," "World of Warcraft" or "Counter Strike: Global Offensive." Though players can't see each other, they can hear plenty.