Ten white crosses with red hearts were also displayed in front of the school to symbolize the eight students and two teachers killed during the mass shooting.
A man from Chicago who travels to mass murder sites to pay tribute to the victims placed the crosses on the campus.
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During the moment of silence, many embraced in prayer. Others bowed their heads solemnly.
President Trump has also ordered that all U.S. flags fly at half-staff out of respect for those affected by the shooting through sunset on May 22.