No. If you'll note, around the final quote you listed, the Brute Captain says, "It's ready to explode if any human gets to close!"
Because of that, killing the Engineer's chaperons triggers its self-destruct sequence. The only way to "save" that engineer is to simply sneak past the Brutes, and to not engage them.
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But they are trying to attach the collar that makes it explode when you get there. Is it possible to kill them BEFORE they actually put the collar on?
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Ah, I see. That would be a no. Even if you maneuver around to back smack the Brute with the charge, it would simply interrupt the animation. From a code/game design explanation, the Engineer always had the charge attached to it.
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