Officials and a Native American tribe in Washington state are offering $13,750 for information leading to the conviction of whoever killed four bald eagles near a lake last week, according to local media.

Authorities tell The Seattle Times they suspect the bald eagles were shot from the trees and dropped into a Snohomish County lake, where their bodies were found floating. The incident occurred east of Granite Falls, the Herald newspaper of Everett reported.

"I've never seen anything like this in 11 years...it's egregious," Sgt. Jennifer Maurstad of the Washington Department of Fish and Wildlife, told NBC station KING of Seattle.

Marustad told The Seattle Times it appears the birds were shot with a small-caliber rifle.

Investigators say the black market for eagle parts can be lucrative, potentially fetching hundreds of dollars, the newspaper reported. Parts could be used in things like high-end artwork or cultural ceremonies, according to The Seattle Times.

"I don't think he (the killer) had any intention of profiting from them," Maurstad told The Seattle Times. "I think it was just a spur-of-the-moment opportunity."

Without a permit, killing a bald eagle -- America's national bird -- is a serious offense.

In the United States, the bald eagle and the golden eagle are protected under multiple federal laws, according to the U.S. Fish & Wildlife Service. Per the Bald and Golden Eagle Protection Act, felony convictions can lead to a maximum fine of $250,000 or two years in prison. Civil penalties are also subject to thousands in fines and imprisonment. Bald eagles are also protected under the Migratory Bird Treaty Act and the Lacey Act. The bald eagle was removed from the Endangered Species federal list in 2007.

The act is also a misdemeanor under Washington state law, according to The Seattle Times.

The Stillaguamish Tribe, a Native American group based in Arlington, Wash., has pledged $10,000 toward the reward fund.

"The Tribe is shocked and offended at the wanton wastage of wildlife and supports the efforts of state authorities to investigate and prosecute this case," the tribe said in a statement Friday.