A King County Metro bus hit the eagle, nicknamed "Eddie" by many, at 7:30 a.m. Tuesday, The Seattle Times reported.
Metro spokeswoman Linda Thielke said the bus was in the middle of the bridge, moving at about 50 miles per hour when the eagle started to fly in the same direction as the bus.
"The bird very, very suddenly took a turn and smashed into the windshield," cracking it, Thielke said.
The driver kept moving and reported the accident shortly after.
The enforcement captain at the Department of Fish and Wildlife, Bill Hebner, said the eagle killed was more than likely the male of a pair that nested at Seattle's Broadmoor Golf Club.
"I think the lesson learned here is, as motorists, whenever you see wildlife along the road ... be cautious, be defensive, slow down and know they will often do the unpredictable," Hebner said.
Although the body of the bird was mangled, its feathers will be delivered to a repository in Denver, and then sent out to Native American tribes, a standard practice when a bald or golden eagle dies.