Jeez! Go to a pay phone, call the PD, and tell the answering party you want to talk to a homicide investigator. Tell 'em WHO is the victim and who the perp is, WHAT you know for a fact, WHY you think this situation is real, WHEN the episode occurred, and WHERE it occurred. State your information briefly and concisely, without discussing how you "feel" about any of it. (You are discussing a reportable incident, NOT a psychic manifestation. Try to sound like a mature, reasonable adult.)

If you sound like an emotional jerk, they will blow it off. If you sound like someone setting someone up for a bogus fall, they will write you off and figure you are filing a false report. (Prosecutable) If you are not organized and concise in your presentation, they will figure you're a nut-ball.

If you initiate the conversation by stating that you believe (give them a name, address if possible) has been murdered. (That is verifiable, we hope) Tell them who you believe the perp is, in detail. (Name, location, etc.) Also verifiable. If you know someone who was a party to the incident, a witness to the incident, or who you have heard talking about the incident, tell them. That gives them some place to go to begin inquiring if a crime has been committed.

If YOU witnessed the act, if YOU were told about it by the perp or someone close to them, the investigator will want a one on one with you. Before agreeing, state your reason for fearing for your own welfare and let them discuss what can be done with that.

Then make your decision to go forward with this, or not.