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Die At One's Post
Die On Duty, Die At Your Post
noun, する verb
If you want to become a martyr during your employment you need to die at your post. I don't know why you'd WANT to do that though.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
The detective took a bullet and died at his post.