Law enforcement sources tell us a friend found Eva's body late Saturday night after having seen her alive Friday morning. We're told the friend had a key to Eva's NYC apartment and when they went to check on her ... they found her hanging inside.

We're told the friend called 911, and when police arrived ... they told police they didn't know Eva to be depressed or emotionally disturbed -- so it's safe to say it took them by surprise.

When paramedics arrived, they pronounced her dead at the scene.

Our sources tell us there were no unusual injuries ... and there was no sign of a struggle. Our sources say a note was left behind, the contents of which are unclear at this point.

Despite the obvious signs of what certainly sounds like Eva taking her life ... we're told her official cause of death hasn't been ruled on just yet, and is pending toxicology results.

The update comes a few days after Eva's sister announced her passing on social media. In her tribute, Lila expressed her grief over Eva's passing ... praising the "Club Rat" creator as a sweet and loving sister. She didn't provide any context or details about her sibling's death.

Eva was known on TikTok for posting day-in-the-life type content about 20-somethings in New York ... and she also famously created a web series called 'Club Rat' about the dating scene.

While she wasn't known for posting about mental health, Eva did share a personal story with an org called Don't Mind Me ... which advocates for folks who are struggling. She revealed her father had died by suicide in 2018 ... something he'd threatened since she was a kid.

She was only 29.

RIP