NASHVILLE, Tenn. (AP) — Nashville Police have “exhausted all available investigative avenues” in the hunt for the person who leaked pages from a school shooter’s journals to a conservative commentator, the department announced in an email sent to media late on Friday. The writings are part of an ongoing legal battle over whether they should be released as public records.

The Metro Nashville Police Department’s Office of Professional Accountability led the investigation into the leak, interviewing officers and forensically examining their electronic devices, according to police. Investigators determined that three cellphone photos were taken of the journals just after they were discovered in the shooter’s vehicle by two detectives with the Specialized Investigations Division. One former police detective who had images from the journal declined interview requests.

“The department does not have the ability to compel statements or cooperation from former employees,” the police statement reads.

The person who killed three 9-year-old children and three adults at a private Christian elementary school in Nashville this spring left behind at least 20 journals, a suicide note and a memoir, according to court filings. The writings have been the object of intense speculation and an open-records battle, with several groups suing to force Nashville officials to release them to the public.

Police initially said they intended to release the writings once they closed their investigation, which could take up to a year. Since then, a group of Covenant School parents have joined the lawsuit, arguing that none of the documents should ever be released. They say shooter Audrey Hale’s writings could traumatize their children and inspire copycats.

In the midst of the legal wrangling, someone slipped images of three of Hale’s journal pages to conservative commentator Stephen Crowder, who published them on Nov. 6. They include a detailed timeline for the March 27 shooting labeled “Death Day” and a slur-filled diatribe about kids who attend “private fancy schools,” although the 28-year-old Hale was a former Covenant student.

The three children who were killed in the shooting were Evelyn Dieckhaus, Hallie Scruggs and William Kinney, all 9 years old. The three adults were Katherine Koonce, 60, the head of the school, custodian Mike Hill, 61, and 61-year-old substitute teacher Cynthia Peak.

Seven officers were assigned to administrative duties when the investigation into the leak began, but all of them have been returned to regular duties, according to police. Police have briefed the director of Nashville’s Department of Law on their investigation and forwarded the case file to the district attorney’s office.