LAUDERDALE-BY-THE-SEA, Fla. -

Broward Sheriff's Office detectives have arrested one man and are waiting for a second to turn himself in three years after a deadly explosion at a Lauderdale-By-The-Sea hyperbaric treatment facility. 

Lance Bark, 51, a medical technician, is under arrest on charges of manslaughter and aggravated manslaughter. George Daviglus, , 82, a doctor, is facing the same charges and is expected to turn himself in later this week. 

It was May 1, 2009, when a fiery blast inside a hyperbaric chamber injured a 4-year-old Italian boy who was being treated for cerebral palsy and killed his 62-year-old grandmother, Vicenza Pesce. The boy, Francesco Martinisi, died several weeks after the incident.  

The explosion made international news. An Italian television station had earlier aired a story showing Martinisi's father climbing into a chamber with him, saying he hoped oxygen therapy would help his boy's condition. 

On Wednesday, police said negligence instead killed him. 

BSO Detective Frank Ilarraza said an investigation showed that Martinisi was not properly grounded and that static electricity started the fire. He also said the machines were not properly maintained. 

"The chamber was dusty inside, and that started a fire inside a chamber," Ilarraza said.

Bark was supposed to be in charge of safety. BSO said he and Daviglus failed.