The Arbites, Herold Ortega, was torn during the argument. On the one hand, he was merely a tool of the Emperor's will, which meant he would follow the Imperial superiors who led him to the letter. However, the Deathwatch Astartes, while speaking of out turn, had a point and voiced what everyone must have been thinking about the Psyker. He was glad the Celestian knew not to condemn the Astartes on the spot, but merely lecture him. They would need the armored super human very soon. 

The group ran toward the armored bunker, the Arbites just beside them. Rain spattered off his carapace armor and dribbled down his half-face helm. He licked his lips, glad that this world didn't have poisonous rain in the atmosphere. His thundering boots thudded into the already ankle-deep puddles as he hustled into cover. Before he arrived in the dryness of the bunker, he had his combat shotgun primed and ready. 

Just as soon as he vaulted over the first window-sill, bullets from shootas ricocheted around him. He grunted and planted himself below the cover, his companion began readying themselves to fire back. Herold checked to make sure he still had his grenades, before he grimly lifted himself off of the ground to face the lumbering and howling Xenos that even now bore down on their position. He lifted his shotgun, aiming the powerful weapon like most guardsmen would aim a rifle. 

Herold was no Space Marine, but he was still imposing for a human, and the kickback from his combat shotgun was minimal in his grip. He fired off a slug, accurately taking an Ork in the collarbone. His next slug punched into the Ork's throat, causing the bestial Xenos to tumble and gasp, clawing at the wet ground in his death throes. Herold pumped the shotgun, and took out the Ork behind that one was well, ripping off apart of its huge head. 

His next few shots were more general in direction, meaning to provide cover fire for the others more than anything. Missiles streaked past his shoulder, courtesy of the Krieger troop and the Astartes. Herold saw this spurred other Xenos to an even greater frenzy, even as their comrades died and their armor was blasted to bit. Herold began to fire more accurately once more, putting slugs into every Ork that made it closer than 30 yards, reloading with a swift, practiced ease when needed.