It doesn't take much to get someone to beat his fellow man silly.
Just give him a weapon: A pillow. And provide motive and opportunity: International Pillow Fight Day.
On Saturday, hundreds of people packing pillows descended on Pershing Square in downtown Los Angeles -- one of some 150 cities worldwide where fights with soft bedding were expected to break out.
The loosely coordinated events were part of the so-called urban playground movement and promoted by Newmindspace, a public art group based in New York and Toronto. The project is intended to show how social media can be used to organize people to embrace urban public settings.
"When you're a kid, a pillow fight is the thing you'd do when your parents weren't around," said Francis Co, 25, of Whittier.
Co came prepared: pajamas, a surgical mask for when the feathers started to fly and eyeglasses without lenses. "People generally don't hit you as hard if you're wearing glasses," he said.
Though there are few rules in pillow fighting -- don't hit children or people with cameras -- there is plenty of strategy.
"You need to look for the weak ones," Co advised.
"If you want to hit a lot of people, stay on the rim," said Phil Holland, 30. Stay away from the middle, where brawlers can inflict a lot of damage. Another piece of advice: "Don't inhale the feathers."
As the appointed time of 3 p.m. approached, waves of people streamed into the square from every direction.
Some clutched ratty, stained things you wouldn't want to lay your head on. Others carried new pillows that still had their price tags.
Elayna Rice, 23, of Studio City prepared by cutting slits into her newly bought pillow to hasten feather flow.
"It'll also make my pillow look tougher," she explained as the time for battle neared. "It's going to get really intense in the middle. You need to just run in and swing at anything that moves."
Across the way, 18-year-old Chris Salvador and two friends were waiting with PMDs (pillows of mass destruction): three couch cushions brought from home without his parents' knowledge.
"These are military-grade," Salvador said. "It's like Mike Tyson locked in a pillow. This ain't a joke. This is a war."
Just then, a guy wearing a bunny costume walked past.
"Oh my god!" Salvador said. "I'm hitting that bunny! Candy's gonna pop out of that guy!"
Little did he know that the bunny, Shaun Shue, was armed as well.
"I'm prepared," said Shue, 25, of Hollywood. He discreetly pulled a pillow out from under his costume and then stuffed it back in. "Nobody knows I've got this yet."
It was impossible to tell who, if anyone, was in charge. But when the time came, there was a countdown from five and the pillows went off across the square like popcorn.
People belted one another with abandon. Feathers swirled like snow. And the streets ran thick with the down of the vanquished.