In the following sentence:

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> 外交部发言人耿爽14日就两名中国公民在日本不幸遇害答记者问时表示，中国驻日本使馆已要求日方全力破案，缉拿并严惩凶手，还受害者及家属公道。“我们对两名中国公民遇害表示沉痛哀悼，对其家属表示诚挚慰问，对凶犯的残暴行径予以强烈谴责。”耿爽说。
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If I understand it correctly, the main clause in the first sentece is from `中国驻日本使馆已要求日方全力破案`, and `外交部发言人耿爽14日就两名中国公民在日本不幸遇害答记者问时表示` is a subordinate clause. And the subordinate clause says something like:

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> When the ministry of foreign spokesman 耿爽 answered to the question by the reporter on 14th,
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However, how does `就两名中国公民在日本不幸遇害` function here? Is it the reporter that asks about the murder crime so the sentence should be like:

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> When he answered to the reporter who asked about the murder crime,
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or is it just added by the author of the post, so the sentence should be:

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> When he answered to the reporter regarding the murder crime,
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? If so why is it not expressed to use some `regarding...` adverbs such as `关于` or `于`?