A Denver Police Department recruit recently had his leg amputated after suffering an injury during an academy training drill.

The city is investigating the rare incident, and sources have told reporters that the recruit may have had a pre-existing medical condition that made him vulnerable to the injury.

According to police, the recruit was rushed to a hospital by ambulance on January 6 after being injured in a “Dynamic Action Drill” at the Denver Police Academy. The drill involved role-playing different scenarios, such as a suspect resisting arrest or attacking an officer.

“That elevates not only the mental stress but the physical stress that a typical police officer would encounter on the street at any given day, at any given time,” Natasha Powers, a former California police officer who owns Powers Police Practices, Consulting and Investigations in Grand Junction, Colorado, told FOX31.

Powers said that police candidates typically undergo a medical exam and a physical abilities test before joining the academy. “No instructor wants a trainee or a person that they’re training to become either injured through some sort of broken bone or have some sort of other major medical event. And the scenarios are designed, like I said, to elevate physical and mental stress, but not to harm the crew,” she said.

Multiple sources reported the man had to have one of his legs partially amputated, and that he may have sickle cell trait (SCT) or another genetic disease. According to the CDC, those with sickle cell trait may develop health problems known as “pain crises” during physically stressful situations such as vigorous exercise.

“The Department remains concerned for him and is in contact with his family to provide support. For the sake of the recruit officer’s privacy, we are unable to provide his name, and due to HIPAA regulations, we do not have a condition to share at this time. DPD initiated a review of the circumstances, which is ongoing, and there is not an Internal Affairs investigation into this matter at this time,” the department stated to FOX31 in an email.

A Denver Police spokesman confirmed that recruits are medically evaluated prior to training by the city’s Civil Service Commission. The evaluation includes a physical agility test and medical exam, according to the executive director of the Civil Service Commission.