A federal judge sentenced a former dive boat captain on Thursday to four years in prison on a negligence conviction known as "seaman's manslaughter" after 34 people were killed in a fire that broke out on his boat in 2019. Jerry Nehl Boylan, who faced up to 10 years in prison, was found guilty in 2023 of one federal felony count of misconduct or neglect of ship officer. The fire erupted on the morning of Labor Day, when the boat was anchored near Santa Cruz Island, the largest of California's Channel Islands, about 25 miles off the mainland. Boylan, 70, was one of five crew members to make it off the 75-foot vessel, The Conception, and the first to abandon ship, according to prosecutors. Thirty-three passengers and one crew member below deck died of smoke inhalation, police said. The victims were sleeping below deck when the fire broke out, according to the US Attorney's Office for the Central District of California. Robert Sumwalt, the chairman of the National Transportation Safety Board at the time, said it was the deadliest maritime accident in nearly 70 years. Prosecutors said Boylan did not attempt to fight the fire or rescue passengers, failed to conduct sufficient fire drills or crew training and did not set a night watch. "As the jury found, this tragedy could have been avoided had Mr. Boylan simply performed the duties he was entrusted to carry out," US Attorney Martin Estrada said in a statement at the time. "We hope that today's verdict brings some solace and closure to the victims' loved ones." Estrada on Thursday said Boylan could have taken steps to prevent the deadly accident. "If this defendant had only trained and drilled his crew on the firefighting equipment that was on the ship ... including hoses, including pumps with a limitless supply of water, if he had trained them to use that equipment, this tragedy could have been avoided," Estrada said at a news conference. "If he had had a night patrol, a basic measure to have someone awake at night to catch if something went wrong, that person could have caught this fire, tried to stop it, tried to warn the victims," he said. Susana Solano Rosas, whose three daughters died in the fire, expressed relief over the conviction but disappointment in the length of Boylan's sentencing. She held up a poster of her loved ones at Thursday's news conference. "I've lost my belief in our justice system that we have here in our country because I would have expected at least 10 years, but we've got to accept what it is," Solano Rosas said. CNN contacted Boylan's attorney for comment but has not heard back. In 2019, an attorney for the boat's owner, Truth Aquatics, said that a crew member had checked the area where the fire was believed to have been concentrated before it ignited. NTSB investigators said the fire may have been caused by cell phones and batteries left charging overnight, though the agency could not definitely determine a cause. — CNN