Severely Injured

Severely Injured is a status.  It's easy to understand what it does, and how to recover from it.

What I'm having trouble finding is how the condition is inflicted/imposed.

Not ruling out that I may have missed it in the vast rulebook.

Could someone please clarify for me how Severely Injured occurs?

You become seriously injured after your Health is reduced to (negative one-half max health) or more.

So if you have 320 max Health, and you're taken down to -160, you're seriously injured.