One Piece Chapter 38, page 20: PIRATE FLEET

The pirates are mercilessly cut down by the invisible attacks. One of them explains in terror, "IT'S NO USE!!! WHEN HE'S USING HIS 'SILENT STEP' ATTACK, HE CAN'T DISCERN ONE PERSON FROM ANOTHER!! HE'S SO FAST THAT EVEN HE DOESN'T KNOW WHAT HE'S ATTACKING!! HE WON'T STOP THAT 'TIL HE'S TIRED!!!" Nami is horrified, shouting, "WH... WHAT'S GOING ON...?! THOSE PEOPLE ARE GETTING MASSACRED OUT OF NOWHERE!!" Luffy gets slashed on the cheek as the slaughter continues.