Lawless Oceans premieres Jan. 10 on the National Geographic Channel
Each product we feature has been independently selected and reviewed by our editorial team. If you make a purchase using the links included, we may earn commission.

In March 2016, special investigator Karsten von Hoesslin took on a daunting task: tracking down whoever fatally shot four people in the middle of the ocean, and figuring out why.

The only information he had to go on? Ten fleeting minutes of chilling footage from a cellphone video that went viral in 2014 on YouTube.

No one was arrested. The killer — or killers — seemed to have gotten away with murder.

Until now.

In the National Geographic Channel’s new six-part series, Lawless Oceans, which premieres Jan. 10, beginning at 9 p.m. ET, von Hoesslin searches for answers about who killed the men. Along the way, von Hoesslin encounters drug smuggling, human trafficking, illegal fishing and piracy — and more.

‘’This video is just the tip of the iceberg in this case,” von Hoesslin tells PEOPLE.

“Since it is still an active investigation, I would not be surprised if the case only became even more dangerous.”

• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.

The series follows the veteran investigator as he travels the world — from Southeast Asia to the Indian Ocean — searching for leads. It all starts with the disturbing video, which shows other men laughing after the victims were shot in the water.

Credit: /Alex Mott/

“It’s the most complex case I have ever worked because a lot of it takes place in oceans that are outside of territorial jurisdictions,” von Hoesslin says.

• Pick up PEOPLE’s special edition True Crime Stories: Cases That Shocked America, on sale now, for the latest on Casey Anthony, JonBenét Ramsey and more.

When he first started investigating the case, he says he had no idea how he was going to solve it.

“But I was pretty persistent and made some really big discoveries relatively quickly.”