As Kim Jeoung-hee huddled in a bomb shelter on South Korea's Yeonpyeong Island, scared and confused with around 250 other people, memories flooded back of the day in 2010 when North Korean troops shelled near their homes. But the alarm was a reminder of how vulnerable Yeonpyeong remains more than 13 years after the bombardment that killed two soldiers and two civilians there, and left an unconfirmed number of North Korean casualties after South Korea fired back. "Every time I hear a bang I get scared," Kim told Reuters on Monday, standing in the same bomb shelter, a bunker buried in a hill with toilets, a small kitchen and blankets inside.