It was 2001.  Brandon Flowers was a bellman in his hometown of Las Vegas.  Guitarist Dave Keuning wanted to leave his job at Banana Republic, so he posted in a weekly ad looking to start a band.  Flowers liked what the ad had to say, according to this article from Rolling Stone:

“Flowers then hopped into his 1992 Geo Metro and headed over to Keuning’s house to get acquainted. They hit it off instantly and before Flowers left, Keuning handed him a cassette tape of five song ideas. The very first one caught his attention immediately and he fleshed it out with lyrics about a jealous guy convinced his girlfriend is cheating on him. “Now I’m falling asleep and she’s calling a cab,” he wrote. “While he’s having a smoke and she’s taking a drag/Now they’re going to bed and my stomach is sick.” Unable to come up with a second verse, he merely repeated the first one again after the chorus. He called it ‘Mr. Brightside.'”

Listen to the rough first version of the song below.  — [eric]