Someone
noun
誰 is who, 誰か is like asking "who?" If you don't know who it is, you just know it's someone.
だれか
The reading comes from the reading you learned with the kanji.
うちの家族の誰かが、母の死にあの善良な外科医が関与していると訴えたんですか？
Did someone in my family accuse that excellent surgeon of contributing to our mom’s death?