Why is the 129th Rescue Wing's flag at half mask?

California National Guard 129th Rescue Wing located at Moffett Field http://www.129rqw.ca.ang.af.mil/ has flown it's flag at half mask for at least a week. The flag on the main part of the base called AMES Research Park has been at it's regular position on the flag pole. I was wonder if anyone knew the reason or what type situations warrent flying the flag at half mask for a week or more?Why is the 129th Rescue Wing's flag at half mask?
I am not sure why they are flying the flag at half MAST not mask

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