I am trying, and failing, to find an appropriate and succinct way of describing an individual's action in occupying a secure building to the exclusion of all others as a protest.

I could say 'he besieges himself' in the building. 'Takes-over' and 'occupies' come close, but do not really explain that he has locked everyone else, including the authorities out.

My usual online sources have failed me, and I feel like there is some word or phrasing that I am missing here. Any ideas?