CEDAR RAPIDS, Iowa -- A California Marine has admitted he helped kill 50 ducks at an Iowa petting zoo two years ago that police say were stoned to death.

The Gazette of Cedar Rapids reports that Shayne Smalling of Twentynine Palms, Calif., entered his guilty plea in writing to a misdemeanor charge of livestock abuse on Wednesday in Linn County District Court. He was ordered to pay a $625 fine.

Smalling is stationed in California.

Smalling and Zachary Kanellis, of Cedar Rapids, were accused of killing the ducks at Bever Park Children's Zoo in June 2008.

Kanellis pleaded guilty earlier this month to third-degree criminal mischief and injury to livestock. He received a deferred sentence of unsupervised probation for two years, and was fined $625 on each count.