A Sunday estimate of the crowd at the “March for Our Lives” rally for gun control in Washington, D.C., on Saturday was much smaller than the crowd estimated by organizers.

Digital Design & Imaging Service Inc. estimated around 200,000 people attended the rally, CBS News reported. Organizers on Saturday estimated 800,000.

Washington, D.C., metropolitan police have yet to release their own estimates.

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The respected imaging firm uses balloons to fly cameras over events in order to estimate crowd size. The service said there was a margin of error of 15 percent for their estimation. The crowd size was largest at 1 p.m., the company said.

The company said the 2017 Women’s March was the largest single-day demonstration in U.S. history, with 440,000 participating. That number corresponds well with city officials' estimates at the time, as reported by The Associated Press.

The march on Saturday was largely organized by student survivors of the Marjory Stoneman Douglas High School shooting in February that left 17 people dead.

The students from that high school have been advocating for gun control laws and have specifically targeted the National Rifle Association and politicians supported by the group.

The “March for Our Lives” rally had sister rallies in hundreds of cities across the world. Many crowd estimates have yet to be determined.