CHICAGO -- A fire department diver looking for a man who fell off a boat into the Chicago River Monday night was separated from his partner underwater and was killed, authorities said.

The Chicago Fire Department said its "prayers go out to the family of Firefighter Juan Bucio." It tweeted that Bucio "tragically passed away answering a call of a person in the water."

The entire Chicago Fire Department's prayers go out to the family of Firefighter Juan Bucio who tragically passed away answering a call of a person in the water near 2600 S. Ashland. — Chicago Fire Media (@CFDMedia) May 29, 2018

The man fell off the boat around 8 p.m. Monday, police said. Bucio was killed and two other divers were injured while searching for the man in the river, which flows through downtown Chicago.

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Bucio was in the water with a dive partner when the partner lost contact with him, fire Commissioner Jose Santiago said.

"During the search, one of our divers became separated," he said. "Immediate search started with the backup divers."

Bucio was pulled from the water and later was pronounced dead at a hospital, Santiago said.

The man who fell off the boat hadn't been found as of early Tuesday. The two other divers were hospitalized briefly.

Bucio, 46, joined the department in 2003 and became a member of its dive team in 2007, reports CBS Chicago.

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He had two children, sons ages 7 and 9. He also had nine siblings, including a brother at the fire department and a sister at the police department, Santiago said.

"Please," Santiago said, "keep this family in your prayers."