In an exclusive interview with INDY Week Thursday morning, N.C. Department of Public Safety Secretary Frank Perry explained how an ongoing investigation into the unexplained death of inmate Michael Anthony Kerr last month led to the dismissal of five prison workers and the resignation of two others.

“There’s a preponderance of testimony and evidence that their conduct and attention was not appropriate,” Perry said, adding that his office will push “expeditiously” for a criminal investigation if necessary.

The agency, which has been under fire in recent years for its treatment of mentally ill prisoners, fired nurses Brenda Sigman, Wanda St. Clair and Kimberly Towery, as well as nurse supervisor Jacqueline Clark and Captain Shawn Blackburn. DPS spokeswoman Pam Walker said three of those employees have since appealed their dismissal.

Meanwhile, nurse Lisa Kemp and staff psychologist Christine Butler have also resigned during the course of the investigation, which includes an internal DPS probe, as well as independent investigations by the N.C. State Bureau of Investigation and nonprofit Disability Rights N.C.

Kerr, 53, was dead on arrival at Raleigh’s Central Prison March 12 when he was transferred from Alexander Correctional Institution in Taylorsville, where he had spent the past month in solitary confinement. Kerr had a history of mental illness. Officials are awaiting a medical examiner’s report to determine the cause of death.

On Wednesday, INDY Week printed the grisly details of a letter penned by a former Alexander Correctional inmate who says he shared a cell block with Kerr in solitary confinement during the last days of Kerr’s life. His letter claimed that Kerr was left handcuffed, covered in his own feces, without eating for six days before prison workers attempted to transfer him on March 12 to Central Prison, the state’s primary mental health and medical facility for male inmates.

The inmate’s account comes roughly three years after an internal investigation at Central Prison disclosed similar reports of prisoners left unattended and unmedicated in fetid, isolated cells splattered with human waste.

Perry said Thursday that he has not spoken with Kerr’s family, but he pledged that his agency would “shine a light” on what led to his death. “Were I a family member, I would be reaching out and demanding an answer as well,” Perry said. “Nobody is more outraged or saddened than I am.”

Prison officials nationwide have faced mounting criticism in recent years for their use of solitary confinement on prisoners, particularly on prisoners with a history of mental illness such as Kerr. In the past, prison officials have said the confinement, which leaves an inmate alone in a cell for 23 hours a day, can be therapeutic in some cases. Mental health experts have contested that, arguing it can exacerbate mental illness or even spur mental illness in prisoners with no history.

Perry said Thursday that he is viewing Kerr’s death as an isolated incident, arguing that he does not believe all uses of solitary confinement to be “unjustified.”

“I do not believe it is happening all over, but I want an answer to that,” Perry said. “I hope with all my professional heart that this is an isolated incident.”

Perry suggested training is the answer to preventing future incidents. Walker pointed out that prison workers in some facilities, even before Kerr’s death, had begun receiving crisis training to help them better work with prisoners with mental illness. Walker said that crisis training had not been performed at Alexander Correctional before Kerr’s death.

Continue to follow this developing story at INDY Week.