On April 20, 2010, a semi-submersible Mobile Offshore Drilling Unit known as the Deepwater Horizon exploded, leading to the largest accidental oil spill in world history. Six years after the spill and explosion, director Peter Berg has teamed up with Mark Walhberg and Kurt Russell to tell the story of the explosion in “Deepwater Horizon.” Before you watch the film, which is set to hit theaters on Sept. 30, here are six facts you didn’t know about the event:

1. BP Claimed A Spill Wouldn’t Occur

In a 52-page plan filed by BP, the company stated that it was “unlikely that an accidental surface or subsurface oil spill would occur.” In the event that something did occur, BP claimed “no significant adverse impacts” would be expected.

2. Transocean Made Money From The Spill

Transocean, the owner of the drilling unit, made a $270 million profit after the explosion and spill thanks to insurance payouts. The profit was due to the rig’s insurance policy being greater than the value of the rig itself.

3. As Of 2015, Oil Was Still Leaking

Five years after the explosion and spill, oil sheens from the spill were still being seen off the coast of Louisiana. 

4. 600,000 To 800,000 Birds Died

It’s no secret that wildlife was affected by the oil spills but the bird population was hit hard. Oceana — an international ocean conservation and advocacy organization — reported that nearly 800,000 birds were killed as a result of the spill.

5. Eleven People Died

While many people onboard the Deepwater Horizon survived the explosion, three days after the incident, 11 people were confirmed dead.

6. Three Parties Were Found Guilty 

In 2014, BP was found guilty of gross negligence and willful misconduct. U.S. District Judge Carl Barbier called BP’s actions “reckless.” The judge put 67 percent of the blame on BP, 30 percent of the blame on Transocean and the remaining three percent on Halliburton. The judge called Transocean an Halliburton’s actions “negligent.”

Deepwater Horizon Here are six things you didn't know about the real Deepwater Horizon explosion which will be depicted in the upcoming film, “Deepwater Horizon.”