(CNN) -- Investigators asked for help Thursday as they searched for a man seen in a mall in Littleton, Colorado, shortly before what they described as a possible attempt to bomb the shopping center on the 12th anniversary of the shooting at nearby Columbine High School. Authorities told reporters at a news conference that the man they are seeking is a "person of interest," and they asked for help from the news media and public in identifying him. No evidence exists so far of a link to the Columbine shootings, Jefferson County Sheriff Ted Mink said, but he acknowledged the possibility was on the minds of law enforcement officials.
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NEW: A Columbine experts says "it's like attacking people ... in mourning"
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The Southwest Plaza Mall reopens as authorities ask for help
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A possible bombing attempt came on the Columbine anniversary
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Propane tanks and a pipe bomb were found, officials say
The incident happened Wednesday at the Southwest Plaza Mall, less than two miles from @placeholder.