As reported in The Brooklyn Paper:

A machete-wielding robber ambushed a teenager on Stagg Walk on July 27 and got away with his phone, wallet, and bicycle, police said.
The 18-year-old victim said he was walking between Leonard Street and Manhattan Avenue at 5 pm when the marauder came out of the shadows wielding the big blade along with a pocketknife.
“Give me everything you got,” the ruffian said, then put the machete up to the victim’s face, per a report.
The victim forked over his phone, wallet, red mountain-bike, headphones, and MetroCard, officers said. The victim told police he did not see where the thief ran off to afterwards. 

I'm taking away three lessons from this story...

1) The perp is resourceful... I mean, a fuckin' machete?! 

2) The perp is probably not from around here, or at least not Greenpoint - there's no G train, what's he doing taking the kid's Metrocard?!

3) Despite Williamsburg's luxury condos, artisanal cocktail bars, and fancy clothing boutiques... It's still Brooklyn!

But seriously, folks: be safe, cautious and aware of your surroundings at all times.