There is no end to the work that needs to be done and, with the Tourist's interior and main systems operational enough to get them all off planet, that work now involves leaving the relative safety of the ship. After all, it wouldn't do to have vital bits of ship fall off mid-flight or to explode once they hit atmosphere just because of some loose screws or minor hull ruptures.

Chekov is checking the external engine casing when he hears Kirk yell.

He immediately runs towards the shout as he draws his gun--an inelegant thing from the ship's armory that he's kept on his person since they crashed on this awful planet. Not something that he actually intended to use.

The Russian reaches Kirk's position and trains his gun on the Lato'li attacker. Even though the alien doesn't look inclined to pause and talk it out, Chekov isn't about to pull the trigger without trying to diffuse the situation another way. "Stop or I shoot!"