It’s not always that you get to see SpaceX CEO Elon Musk’s raw reaction during a historic event of his spaceflight company. In the National Geographic’s MARS series finale’s never-before-seen footage, Musk was filled with excitement as SpaceX successfully landed their rocket for the first time.

The almost four-minute video is now uploaded to YouTube. NatGeo documented the first stage of the Falcon 9’s rocket landing in Florida. Musk was shown to be watching the said event back on Dec. 21, 2015. According to Mashable, Musk originally thought that the rocket actually exploded before it even reached the ground. Apparently, he mixed up the sonic boom of Falcon 9’s re-entry for an explosion.

Hence, he was evidently freaking out as he uttered, “This is bad!” However, that changed as the rocket stood upright back at Cape Canaveral. He can be heard saying in the video, “What? Holy smokes, man.” Teslarati reported that in a rare caught-on-tape moment, Musk very happily exclaimed, “It’s standing up!” To wrap up SpaceX’s momentous success, Musk high-fived the members of the team.

It should be noted that previous attempts of SpaceX to land Falcon 9’s boost stage failed. In fact, they even tried to set it down on a floating drone ship. Mashable further reported that the company has already managed to safely bring back six more boosters to Earth since last year’s milestone.

As of the present, SpaceX’s next launch has been pushed back until early next year. The company initially said that it would be able to resume by December. However, they decided to postpone it since they are still “working to complete the final steps necessary to safely and reliably return to flight… with the launch of Iridium-1”. The delay might also be driven by SpaceX’s failure to finalize their probe on the Falcon 9 rocket explosion back on September. They need to determine what exactly caused the rocket to explode.

Apparently, the Federal Aviation Administration (FAA) will not issue SpaceX its license to launch unless they complete their investigation. According to Wired, a spokesperson for FAA pointed this out, “They have not completed their investigation and therefore they do not have a [FAA launch] license.”

The footage of Musk’s reaction during the Falcon 9’s successful first landing was seen on NatGeo’s six-part docudrama called MARS. It premiered on Nov. 14 both on the National Geographic channel and FX. The series was based on Stephen Petranek’s 2015 book titled How We’ll Live On Mars. It’s not surprising that Musk is part of MARS since he has been vocal of colonizing Mars by 2024. Furthermore, he wants SpaceX to be the first to send unmanned spacecraft to the Red Planet by 2018.