A common trope in western movies is that, during a quick draw, the one that draws his gun first will shoot last.
While clearly written to give the hero a moral as well as a strategic advantage, there was actually some scientific fact to this trope, as muscles reacting move faster than muscles that act.
So, being the second to reach for his gun, Reave had his weapon raised and levelled at Seth faster than Seth had his two guns aimed, and pulled the trigger without having time to think.
The bolter round was huge, and fast. With the gun on semi-automatic, three rounds were fired, each one trailing blackness behind it as part of Reave's ability, being from the Shadowlance clan, granting each round fired from Reave's bolted the abilities of Shadowlance rounds in addition to their actual design.
Shadowlance rounds were designed for the killing of magical beings. The black aura devoured magic, psychic abilities, tearing through anything more interesting than rocks, no barrier or pocket dimension was safe from then all-consuming effect of the Shadowlance.
It dimly occurred to Reave that maybe it was better to ask questions before shooting strangers, but most people aiming guns at a Marine deserved what they got.
Locke ducked, crushing the handgun under his kneecap as plasma burst over his head. He didn't swear, or make anything more than a grunt to betray his irritation, but instead he did the maths.
The scorch marks in the walls to his left and right, he considered them and did the trigonometry before rising to his feet and returning fire.
Bolter rounds should make short work of that armour, but if they had plasma technology, then there was a chance that they could potentially block the standard bolter round.
So, he switched ammo clip, using Kraken Pattern Penetrator Rounds instead. Replacing the standard exploding core with a solid adamantine core, and using a more powerful charge behind it, The KPP Round flew with a far greater velocity than the standard Bolt. Upon impact, the outer shell peeled away to reveal a powerful, spinning adamantine drill that bored through even heavily armoured mechs. Under heavy fire, Krakens could potentially even take down Terminators.
Nothing human could withstand this. In exchange for the explosion of shrapnel that followed the standard bolt, KPP's could pierce granite like it was paper.
Scott approached the survivor, lifting him into the air. "Answer my questions, whelp." He ordered, planting a psychic hearing aid to the side of the crying man's skull. "And you may yet live."
Slim scanned the document, matching it with the copy he was shown during the briefing. "Same reason I'm here." Slim nodded. "Alright, I'm Slim, good to meet you." He said with a grin, extending a fist to bump with her.