Childermass had indeed paused to discuss something with the driver, something about Mr Norrell's security, which he would have ensured if Mr Norrell had not wandered off on his own as he had. Childermass had been wary of the other man's disappearance but had not thought too much of it. At least not until the shouting had started. Screaming, he should say. In distress. Of his name.

He breaks into a run in the direction of Norrell's voice, and as he rounds the corner, the first thing he sees is the gun, armed and raised towards the other man. So he acts without thinking. Throwing a hand out towards the gun and pushing his magic through towards it as well, grabbing it and pulling it up and away from Mr Norrell, and out of the other man's hand if he doesn't have a good enough grip on it.

"You will let him go!" he growls at Norrell's two attackers.