Three Florida correctional officers were arrested on murder charges for allegedly beating an inmate to death, while a fourth remains at large, authorities said Thursday.

Christopher Rolon, 29, Kirk Walton, 34, and Ronald Connor, 24, were arrested Thursday following a monthslong investigation of the fatal incident at the Dade Correctional Institution in Miami-Dade County, the Florida Department of Law Enforcement said.

They were arrested on multiple charges, including second-degree murder, conspiracy, aggravated battery of an elderly adult and cruel treatment of a detainee, jail records show. Attorney information was not immediately available.

Additional information on the fourth correctional officer being sought by law enforcement was not provided.

The incident occurred on the morning of Feb. 14, before the inmate was scheduled to be transferred to a correctional facility in Lake County, according to the Florida Department of Law Enforcement, which led the investigation into the death along with the Miami-Dade State Attorney’s Office.

After the inmate reportedly threw urine on an officer, he was placed in handcuffs and removed from his cell in the mental health unit, at which point the officers “began to beat him,” the Florida Department of Law Enforcement said in a statement.

“The inmate was beaten so badly he had to be carried to the transport van,” the agency said.

The inmate, whose name was not released by the agency, was placed in a compartment of the van alone. During a stop in Ocala, an over 300-mile drive from Dade Correctional Institution, he was found dead, authorities said.

The inmate’s death was caused by a punctured lung leading to internal bleeding, according to the Florida Department of Law Enforcement. He also had injuries to his face and torso “consistent with a beating,” the agency said.

The incident initially led the Florida Department of Corrections to place 10 officers on administrative leave. One officer also resigned over it, the department said.

“What happened in this case is completely unacceptable and is not a representation of our system or of Dade Correctional Institution as a whole,” Florida Department of Corrections Secretary Ricky Dixon said in a statement Thursday. “The staff involved in this case failed, and as an agency we will not stand for this.”

The Miami-Dade State Attorney’s Office, which is prosecuting the case, is holding a press briefing Friday afternoon with the Florida Department of Corrections and the Florida Department of Law Enforcement to share further details on the criminal charges.

“Staff misconduct, abuse or criminal behavior have no place in Florida’s correctional system,” Miami-Dade State Attorney Katherine Fernandez Rundle said in a statement. “Inmates should not be subject to forms of ‘back alley’ justice which are actions in violation of Florida law.”