Uncle Jimbo's Get Mediaeval
|"Downward and onward!"|
Skill Challenge: Gather Evidence of a Crime
Door knocking is basically Streetwise and Diplomacy. Maybe an Endurance check could cancel a failure on one of these skills, or Insight could save a success.
Perception to search a scene (maybe Athletics if clues are in inconvenient places or Nature if soil, plants, animal feeding or weather are factors). Heal to draw conclusions from injuries on the bodies. History to know pertinent facts about the locality or the victims.
Interrogating a suspect requires Intimidate (or they could attempt a Bluff, but that could have bad effects if failed). Questioning a frightened bystander is more likely Diplomacy.
If magic or spirits are involved, Arcana and Religion checks may contribute (but maybe require an Insight check or three Heal or Perception successes first to realise that something unusual is going on and unlock these skills).
After the players have a reasonable number of clues (say, half the total) they could use Insight for profiling or Stealth and/or Thievery to follow someone unnoticed.