Four crew members of the sunken South Korean ferry were indicted on homicide charges Thursday.

Sewol ferry captain Lee Joon-seok, the chief engineer, and the first and second mates have been charged with murder, and could face the death penalty for their crime.

Prosecutors held the senior crew members primarily responsible for the deaths of 281 passengers and crew, and the presumed deaths of 23 unrecovered persons. 11 other crew members were charged with negligence for their actions during the April 16 sinking.

Investigators found that the vessel was overloaded and the ballast tank—which maintains a floating structure's center of gravity—was inadequately filled. The Sewol capsized on its way to Jeju from Seoul with 476 people on board. Only 172 passengers and crew survived the disaster.

Almost immediately after the Sewol's sinking was reported in the media, stories of the crew abandoning ship began to spread. While 339 students and teachers from Seol's Ansan Danwon High School were told to stay in their cabins, crew members, including the captain, were caught on videotape leaving the ferry.

Prosecutor Ahn Sang-don said that their actions were inexcusable.

"The captain, a first officer and second officer and the chief engineer escaped before the passengers, leading to grave casualties," he told reporters. "The captain should have been in command of the navigation, but left that to a third officer, and that is gross negligence."

Ahn also said that crew members confessed "they were thinking about their own lives," but should have put their passengers first.

"The charge of homicide was applied because they did not exercise their duty of aid and relief, leading to the deaths of passengers," the prosecutor said.

Three people were arrested last week for improper handling of the Sewol's cargo, and one executive was arrested for improper financial dealings with Chonghaejin, the company that owns the ferry.

Prosecutors are also investigating the inspection agency that cleared the ship, the ferry operator, and the family that owns the ferry. Officials say the head of the family, who lives in the United States, may be extradited to South Korea.