Spencer Locke is in the middle of a scary situation ... someone is threatening to rape and shoot her, and cops are on the hunt to find the suspect.

LAPD sources tell TMZ the 'Resident Evil' actress reported some creep who left the following disturbing message on her Instagram: "I'll rape you Spencer Locke I'll f*** your brains out then I'll use a pillow put it over your face then I'll pull the trigger then I'll cry."

We're told cops haven't been able to track down the IG troll yet, but have a search warrant to obtain the person's IG account information. They're planning to bring in the suspect for questioning.