I was built for it.

[It means that very literally, but it doesn't explain further. With the gun-arm visible, the conclusion is probably easy to draw. It does at least fold the forearm weapon back down as it holds the dagger out, hilt-first, for Maggie to take back.]

Charging back past those things is a last resort. They haven't tried to break through [yet] but they're probably waiting on the other side of the door.