According to forum Singapore HardwareZone, an older woman called the police after seeing a cosplayer dressed as the character Ryuko Matoi from popular anime Kill la Kill. The outfit was Ryuko’s battle gear, which displays underboob.
HardwareZone commenters say that the older woman was apparently attending a church service (or event) in the same convention center and was offended by what she saw.
Website OnePixelJump reports the two got in an argument over the costume and that resulted in the police showing up. Apparently, no one was arrested, though the cosplayer was reportedly shaken by the entire incident.