The individuals were parasailing shortly before 5:30 p.m. when the vessel's tow line snapped, causing them to drag across the water, according to a Florida Department of Law Enforcement incident report.
The winds had "picked up" and the parasail struck the Old Seven Mile Bridge near Pigeon Key, the Florida Fish and Wildlife Conservation Commission said in a statement Tuesday.
According to an incident report from the FWC, a strong gust of wind "pegged" the parasail, which is jargon for when the parasail chute becomes controlled by the wind speed rather than the operation of the vessel.
When this took place, the captain "cut the line" that was tethered to three parasailers," who then "dropped from an unknown height and dragged through the water by the inflated parasail," according to the FWC incident report. "The chute continued to drag the victims through and across the surface of the water" until the collision, the report stated.
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The woman and one of the boys were unconscious following the collision, police said. A good Samaritan helped bring the three individuals to a nearby dock, according to the incident report.
That good Samaritan, fishing boat captain John Callion, was on a charter boat nearby when the parasail lost control and raced toward the bridge.
"I thought they had it under control first. But, for a minute, my customer's like, 'What's going on? What are they doing?' I'm like, 'It looks like they're trying to figure out a plan to rescue these people,'" Callion said. "And then 30 seconds goes by, which seemed much longer, and nothing was changing. So then that's when we sprung into action."
Alaparthi was still attached to the children in a harness when she died.
"The kid, he was letting me know, 'Help me, help me,'" Callion said. "We got him in the boat immediately. And then we got the other kid that was unconscious. And then we got his mom in the boat."
The Coast Guard said in a statement that Station Marathon boat crews, partner agencies and a good Samaritan recovered a deceased woman and rescued two children on Monday. The good Samaritan arrived on the scene, took the three parasailers aboard and brought them to Sunset Grill Marina where they were transferred to EMTs, the Coast Guard said, and were then taken to Fisherman's Hospital in Marathon.
The woman was pronounced dead at the scene after first responders attempted life-saving measures, police said. The boy regained consciousness and was transported to Miami Children's Hospital for treatment, authorities said. His current condition is unclear. The other boy suffered minor injuries, authorities said.
"Our condolences are with the family and loved ones of those affected by Monday's accident," Capt. Jason Ingram, Coast Guard Sector Key West commander, said in a statement. "This was a tragedy for a family seeking to enjoy their visit to the Florida Keys. Our team, and our partners at Florida Fish and Wildlife Conservation Commission, are investigating the accident to determine the causal factors and mitigate future casualties to make the waterways as safe as possible."
There were between 10 to 12 family members at the scene, including the woman's husband, according to the incident report.
The victims were from Schaumburg, Illinois, and had been on a parasail ride with Lighthouse Parasail, based in Marathon, according to the Florida Fish and Wildlife Conservation Commission. The FWC incident report identified the woman as Supraja Alaparthi.
ABC News did not immediately hear back from Lighthouse Parasail for comment.
ABC News' Cherise Rudy, Matt Foster and Darren Reynolds along with our sister station WLS contributed to this report.