28-year-old Audrey Hale -- who identified as a man with he/him pronouns, and who apparently started using the name Aiden of late -- was a graphic artist and illustrator ... and Hale's AH Illustrations website is now being pored over in the wake of the massacre.

As you know ... authorities ID'd Hale as the person who killed six people Monday, including 3 kids and 3 adults with an AR-15-style gun. A motive is unknown, and Hale is dead now too.

Because of the inexplicable carnage ... folks are looking for answers anywhere they can -- including in Hale's artwork, which has gone under a microscope in the wake of the tragedy. One piece, in particular, has made some feel like Hale was telegraphing sinister intentions.

It's a digital drawing of Jack Nicholson as Jack Torrance from Stanley Kubrick's famed 1980 horror flick ... the shot of him looking crazed as he stares out the window, specifically.

There's more to the disturbing creation, including the notorious phrase "REDRUM" ... which is "MURDER" spelled backward and which was heavily featured in the film. That phrase is prominently displayed in Hale's art, as are other quotes and phrases from 'The Shining.'

Aside from this, Hale's art is mostly innocuous and interesting. Hale's bio is also pretty mellow -- describing Hale as a freelance artist whose art attempts to bring a "whimsical and light-hearted feel."

Hale talks about enjoying video games, watching movies and playing sports ... going on to say this, "There is a child-like part about me that loves to go run to the playground. Animals are my second passion, so I also enjoy spending time with my two cats."

A self-portrait says Hale's on a "mission to change the world." Cops say Hale left a manifesto behind, although its contents haven't been revealed. Hale was armed with two rifles during the onslaught, and law enforcement has indicated more weapons were at Hale's home.