CHICAGO (CBS) — Video of fallen Chicago Firefighter Juan Bucio’s final moments is raising new questions about the rescue operation that cost him his life Monday night in the Chicago River.

Bucio disappeared under the waves of the river near 26th and Ashland while searching for a missing boater, and was pronounced dead after he was pulled out several minutes later.

CBS 2 was on the scene as rescue crews tried to locate Bucio under the waves, and eventually pulled him from the river.

Fire Department dive teams responded to a call about a man who fell off a boat shortly before 8 p.m. Monday on the Chicago River near Canalport Riverwalk Park.

A helicopter dropped Bucio and his partner into the river to search for the boater. The two had been in the water for some time when they began swimming to a Chicago Fire Department boat.

CBS photographer Scott Placko was videotaping the river rescue effort when Bucio and his partner ran into trouble, and crews on the boat began yelling out to them.

“Diver let’s go. Diver let’s go,” a firefighter shouted from the boat.

Bucio and his partner were face to face in the water next to the rocking boat when Bucio’s head went under the waves. His partner placed his hands on the side of the boat to keep his head above water.

Crews on the boat threw a rope to Bucio’s partner. As he was pulled out, there was still no sign of Bucio.

Fire Department radio traffic revealed crews realized Bucio had yet to surface.

“He doesn’t know what happened to Juan,” someone said over Fire Department radios.

Still unsure of what happened to Bucio, crews talked to his partner.

“They were face-to-face at the front of your boat. … He ripped his mask off and then he went down,” someone said over Fire Department radios.

Three minutes passed before other divers entered the water to find Bucio. His body was pulled out after several minutes. An ambulance took him to Stroger Hospital, where he was pronounced dead at 10:02 p.m.

The chief in charge of safety for the Chicago Fire Department watched CBS 2’s video from the scene on Tuesday, but did not comment, including on questions about the apparent 3-minute delay before other divers were sent into the water to look for Bucio.

Meantime, the boater firefighters were searching for, 28-year-old Alberto Lopez, has not yet been found. Friends said the father of three fell off a boat in choppy water on the river Monday night.