Dylan Okimoto and his daughter were barbequing at the park when the bird battle broke out overhead.
"I had no idea what was happening," Okimoto said. "Wow they're two eagles."
That's when he pulled out his camera and started recording.
"Boom, there's the first attack," he said. "This is just incredible."
The Fourth of July fight was between two bald eagles, with one dive-bombing the other.
After the fight, the larger of the two eagles swooped down to the lake while kids were swimming. One of the kids said the eagle got so close she could feel something hit her head.
"Six-foot wing span, seriously sharp talons, they were that close to the kids in the water," Okimoto said.
Okimoto later filmed the smaller, injured eagle swimming to the shore.
Raptor expert Tim Brown, who has returned injured eagles to their nests for nearly 40 years, took a look at the video and offered his own opinion.
"It was a little fight," he said. "It was a skirmish."
Brown noticed one of the eagles was bleeding after the fight and said that wouldn't be the case if the birds were mating. He also said if it was a fight over food, one of them would have had a fish, which wasn't the case.
"I think it was a territorial issue, because you've got nests at Seward Park and nests at Mercer Island," he said.
Brown said eagles are known to duke it out over nesting trees and space. He also said those swimming kids may have actually helped save the injured bird, because the attack could have been even more brutal if people were not around.
Okimoto said after the stunned and bleeding eagle swan to shore, it flew away.