Multiple people were hospitalized and one man is dead following what officials are ruling an accidental carbon monoxide poisoning Sunday.

According to the Berrien County Sheriff’s Department, officials were notified of an unknown medical emergency on a boat in Lake Michigan off Jean Clock Park. First responders located three victims in the boat and all three were transported by Medic One to Lakeland St. Joseph.

According to the release, Lakeland Hospital pronounced one victim, Leonard Anthony Russian, 53, of Cass County, dead on arrival.

Lorri Lynn Mroz, 45, of Cass County was treated at Lakeland Hospital for carbon monoxide poisoning.

Captain Robert Boyce said Russian and Mroz both had Niles mailing addresses.

Richard E. Cook, 63, of Granger, Indiana, was transported to Grand Rapids for further medical treatment.

Several first responders were also admitted to Lakeland Hospital to be treated for carbon monoxide exposure.

The incident is currently under investigation by the Berrien County Sheriff’s Department, and further updates will be provided when available.