Why do otters attack humans?

With at least three otter attacks in the past three years, are Singapore's otters getting more aggressive, and why? Their latest victim, David Andrada, was heading home when he was attacked by a gang of otters two weeks ago. The incident left him with gaping wounds on his thigh, calf and finger. He needed a three-hour surgery, around 10 stitches and spent five days in the hospital. CNA's Rebecca Metteo goes on the hunt for Singapore's cute but vicious critters -- the smooth-coated otters.