Hello, I'm not a teacher.
Where did this passage come from?

Interested in Language
"He has various postures with the gun—half-staff, half a crook for his elbows when it is over his shoulders. He will turn, suddenly realizing she is watching him. He is a survivor of his fears, will step around anything suspicious, acknowledging her look in this panorama as if claiming he can deal with it all. "
What does half-staff mean?
Hello, I'm not a teacher.
Where did this passage come from?
The English Patient. Michael Ondaatje.
Is there anybody knows something about"half-staff"?
Please help me ~~~~>_<~~~~