According to the Birmingham Audubon Society, the Department of Justice (DOJ) is conducting an investigation into an incident at an Alabama island in which hundreds of federally protected birds were killed.

In a news release on Tuesday from the Audubon Society, the group said they discovered on July 10 that visitors on Sand Island’s beach constructed a makeshift volleyball court on top of the breeding ground for Least Terns – the species of the affected birds.

The parent birds, whose bodies shield their unhatched young from the hot sun, were forced to flee their nests by the still-unknown perpetrators, Katie Barnes, coastal senior biologist for the Audubon Society explained in the release.

When employees of the group arrived at the island, they discovered small piles of lifeless-eggs arranged decoratively around wide mounds of sand.

“What was really sad,” Barnes added, “[is] there was a bird that was still trying to incubate her egg in that pile.”

Only 83 baby birds were born out of 600 nests on the Alabama island this season. Each nest contains one to three eggs.

The Audubon Society outlined in the release that their members returned to the colony immediately after the discovery to erect federal warning signs provided by the U.S. Fish & Wildlife Service and fence off the colony with neon yellow rope and metal posts.

The group also reported the incident to the federal agency because Least Terns are federally protected under the Migratory Bird Treaty Act.

Now, the DOJ is reportedly leading the investigation into the incident.

All is not lost for Alabama bird watchers. When the Audubon Society left the island on July 11, approximately 1,200 actively nesting Least Terns and a handful of Black Skimmers still lived there.