Vanessa Guillén, the Fort Hood soldiersince late April, was murdered and dismembered by a fellow soldier, a woman alleged in a criminal complaint obtained by CBS News.
The complaint was not filed against Specialist Aaron Robinson, a suspect in Guillén's death, because hewhen approached by authorities on Wednesday. But the documents accuse Cecily Aguilar, a 22-year-old civilian identified as Robinson's girlfriend, with one count of conspiracy to tamper with evidence.
The complaint says Aguilar told investigators that Robinson said he'd killed a female soldier by hitting her in the head with a hammer, and that the pair dismembered and disposed of Guillén's body near a river.
Aguilar has since been arrested, the Bell County Sheriff's Department confirmed to CBS News.
Guillén was last seen on April 22, when she went to a storage room for weapons and equipment controlled by Robinson, according to the complaint.
In May, two witnesses cited in the complaint said they saw Robinson pulling a large box with wheels "that appeared very heavy in weight," coming out of the same room where Robinson worked. They said Robinson put the box in his vehicle and drove away.
Robinson's phone records, cited in the complaint, pointed officials to an area near where "what appeared to be human remains" were discovered on June 30.
Later that day, Aguilar allegedly told investigators that Robinson had said he'd killed a female soldier by striking her multiple times in the head with a hammer, and put her remains in a box. She allegedly added that Robinson picked her up at a gas station and took her to the site and showed her the remains. Aguilar later identified the remains as Guillén's.
She added that they dismembered Guillén's body and tried to burn it, and eventually placed her remains in three separate holes, according to the complaint.
The remains found at the site have not yet been officially identified as Guillén's, Fort Hood Senior Commander Major General Scott Efflandt said at a news conference earlier Thursday.
Guillén's family has said they believe the remains are hers, and that she told them she was sexually harassed on two separate occasions by superiors. But Efflandt said the investigation hasn't found a link between the allegations and her disappearance.
Aguilar will appear in court next week, according to the Department of Justice. If convicted, she faces up to 20 years in federal prison and a maximum $250,000 fine.