Killer in Purple is a 3D first-person "William Afton simulator". Unlike traditional FNAF games where you survive against animatronics, this fan game puts you in the role of the antagonist, (the Purple Guy).
If you cannot find "Killer in Purple 1" on the official Google Play Store or a verified platform like itch.io, it is likely a fan project or a scam. Do not enable "Install from Unknown Sources" for suspicious files.