ながら used with 中 and を used with だ

Question

Could someone please explain the grammar in the following sentence? I'm particularly interested in the を解決中だ portion.

手がかりを追いながら、数々の難事件を解決中だ。

I suspect that this might be a set grammatical pattern because it seemingly disobeys two that I am aware of. I am under the impression that ながら can only be used to describe two simultaneous actions (where the first is assigned a higher priority in the mind of the speaker). This sentence seems to be using it with だ. Further, there doesn't seem to be a verb that 難事件を could be the object of.

My best guess is that 解決中だ is an alternate way of expressing 解決している or something like that.

Answer 1

suru-verb/noun + 中 forms a no-adjective that roughly means "now ～ing". See: What is the purpose of 中 in ダウンロード中?

• 発売中 on sale
• 故障中の自動販売機 a vending machine that is out of service
• その書類は確認中です。 The document is under review/verification.
• ファイルをダウンロード中… Downloading files...

難事件 is the object of 解決(する). So 数々の難事件を解決中だ means either "He is (in the process of) resolving multiple difficult cases (simultaneously)" or "He has been (recently) resolving many difficult cases".