Published: Jun 26, 2014 2:29 PM EDT

COLLIER COUNTY, Fla.- Collier County Sheriff's deputies have made a second arrest in the case of the murdered Marine, Christopher Corey.

Mallory McCann, 22, was arrested yesterday for robbery with a firearm.

Corey and his two dogs were found dead in his home on Holland Streetback in January of this year. McCann was originally a witness in the botched robbery and shooting death, but investigators learned she was allegedly involved in the plan to rob him.

According to McCann's arrest warrant, deputies found an AK-47 in a pond they searched off of Floridian Avenue. The ammunition loaded in the rifle matched what was found at the murder scene.

Schuyler Morris was already arrested in connection with Corey's death. He remains in jail.