The on again, off again avant-garde art exhibit in Beijing has been closed a second time by police because a newspaper received a letter saying bombs would be placed in the gallery if the show continued. Police closed the show the day it opened, Feb. 5, when a woman shot her sculpture with a BB gun in defiance of a ban on performance art. The artist and her boyfriend were detained for three days and then released, and the show reopened. Organizers suspect an artist who was not picked to take part in the show was behind the bomb threat. "It seems to be another kind of performance art," said one organizer.