04/17/2014 at 09:00 AM EDT
A socialite who was found dead
in her home in this Colorado resort town was killed by a blunt force injury to her head, the Pitkin County coroner said Wednesday.
Nancy Pfister, 57, was hit with a hard object that had a small, curved shape, and she had been dead about 36 hours before her body was found
on Feb. 26, coroner J. Steven Ayers said.
Prosecutors have filed first-degree murder charges against three people
, including a couple who had rented Pfister's home while she was in Australia. William Styler III, 65, and his wife, Nancy Styler, 62, were arrested March 3 after moving out of the home on about Feb. 22.
Katherine Carpenter, 56, an assistant to Pfister and a bank employee, was arrested March 14. Authorities said she called 911 to report she found Pfister's body in a closet of the home.
Investigators have been tight-lipped about the case, and key court documents have been sealed.
Ayers said his office wasn't covered by the court order sealing the files. His report contains some of the only details about the case to be made public.
Prosecutors have filed a motion to unseal other documents, saying no more arrests are expected so there is no longer a reason to keep the files closed. Some media organizations have also asked the court to release the documents.
Defense attorneys have told the judge they oppose the release.
Pfister was the daughter of the late Betty and Art Pfister, longtime prominent Aspen residents who co-founded the Buttermilk ski area west of town. Buttermilk Mountain has hosted the Winter X Games multiple times.
Pfister's death was the first homicide case in Pitkin County in 12 years, not counting those classified as murder-suicides.
The Stylers and Carpenter are being held without bond. They are scheduled to return to court April 23.