BRAINTREE (CBS) – A worker from Texas died inside a Braintree water tank Thursday morning after his equipment failed, cutting off the diver’s air supply.

Town officials confirmed the man’s 14-year-old son was on the ground at the scene when the tragedy unfolded.

“It’s a tragic day. It’s a difficult day for us,” Mayor Joseph Sullivan told reporters.

A spotter jumped inside the tank to try to rescue his co-worker when he noticed something was wrong, but he was quickly overcome by the 45-degree water.

Rescue crews were able to pull him to safety in the dangerous conditions. He was taken to the hospital and treated for hypothermia.

With bone-chilling winds whipping 70 feet above the ground and water quickly freezing on top of the tank, Fire Chief Jim O’Brien said draining the one-million gallon structure would be the safest way to recover the body.

“We gave our best effort,” O’Brien said, commending his crews on the life-saving work. “The gentleman was completely soaked. He was numb. He had no body strength at all.”

Kentucky-based Pittsburg Tank & Tower Group was hired for the inspection, conducted once every five years at each of the town’s five water tanks.

Federal records reviewed by WBZ indicate only one “serious” safety violation in the past decade, according to OSHA’s web site.

Pittsburg Tank & Tower subcontracted the inspection job to TK Potable Diving, located in Texas.

Neither company responded to requests for comment on Thursday. The victim has not been identified.

Sullivan expressed his condolences to the victim’s family and said he was providing “a valuable service to the community.” The mayor also lauded first responders for the rescue effort he witnessed.

“Our fire department worked in incredible fashion with a deep sense of commitment and energy to their task,” he said. “They saved somebody today.”

Investigators will now try to determine how a task routinely performed all over the country suddenly turned tragic.

The water will likely be completely drained from the tank by Friday morning.

Sullivan said there is no threat to the town’s drinking water supply.

WBZ NewsRadio 1030’s Doug Cope reports

