When ruthless alien killers with chameleon abilities escape to Earth, an elite, combat security officer must kill or recapture them before they slaughter the humans that get in their way

Agree with all comments. I would change the "cause the ship's captain to lose..." to something about the protagonist. Or make the ship's captain the protagonist.

I would just go with saving human lives though. Although you can have a nice internal/external struggle between getting the money and saving people. Is there a way to link the two? If humans are killed they lose their commission?

When three shape-shifting alien killers escape his ship and head to Earth, the ship's security officer must hunt them down before their desire to kill costs the whole crew their commission.

"When three killers with Chameleon?powers escape to earth, a (insert adjective)? ships security officer must capture the dangerous fugitives but under no?circumstance?reveal to the indigenous?humans he's an alien."

Agreed with all the above comments.

You describe three separate goals - stop the slaughter, save his job, and avoid jail time, but what's his primary goal?

Tip; It can't be all three, which ONE goal MUST he achieve before the end of the story?