PHOTOS: Charleston shooting and its aftermath
Earlier in the day, the church where the shooting took place, Emanuel AME, held its first service since the shooting. Hundreds of people stood and prayed outside of the church as parishioners mourned and comforted each other inside. The church's pastor, the Rev. Clementa Pinckney, was among the victims.
Hours later, an estimated 20,000 people from all over the country showed their support for the church as they marched hand in hand across the bridge. Organizers called it the Bridge to Peace event.
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Two groups marched from either side of the bridge, meeting in the middle. The crowd was so large that not everyone made it onto the bridge, ABC affiliate WCIV reports. When they reached the middle, they held a moment of silence for nine minutes.
The marchers also prayed, cheered and sang, WCIV reports. There were high fives and hugs. Cars along the bridge and boats traveling below showed their support by honking. The marchers chanted together, declaring, "We are Charleston strong."
The group was led by members of the victims' families, alongside Charleston police chief Carl Ritchie.
Funerals for the nine people killed in the shooting will be held throughout the week.
The Associated Press contributed to this report.