Watching Twin Peaks: The Return. Tulpas are revealed.
The Tulpa gets activated via a specific text message sent to it's phone. When it received the text it recalled a repressed, traumatic sexual assault, and attempted to carry out a programmed mass killing.
The killing was thwarted, and the Tulpa disappeared back to the other dimension from whence it came; where it was born of sexual trauma, and made for one purpose. No history prior to its manufacture. It never existed until created for this purpose by agents of the Black Lodge. Pure evil.
Good show.