My next-door neighbor confessed to schizophrenia, but what he hid in his phone revealed something far more dangerous. WARNING ⚠️ GRAPHIC

I’m writing this because I need to get the full story out of my head, and honestly, I need advice and validation after realizing how close I came to a nightmare.
It started when I moved into my apartment a while ago. My next-door neighbor, "Mark" (31M), was always outside. I noticed he didn’t seem to have many friends or connections, and since I was in an isolated spot in my life too, I reached out. Right away, he told me he had schizophrenia. Having studied psychology growing up and having friends with the condition, I wasn't bothered by it.
We started spending more time together, and eventually things became intimate. Looking back, I was struggling with my own PTSD and self-destructive patterns, which made me vulnerable to what came next.
It didn't take long for his true dynamic to show:
Sexual Degradation & Power Complex: He began using sex as a tool for power. He called me an "object made for his pleasure." Outside the bedroom, he would openly belittle me in front of others, calling me names like "dumb ****." He had zero awareness or care that this was deeply fucked up.
The "Nice Guy" Mask: Despite this, when he wasn't being degrading, he acted incredibly sweet. Once I started hanging out with him, his apartment suddenly became the local "hangout spot," and he built up a circle of acquaintances.
Coercion & Manipulation: Whenever I tried to communicate boundaries or talk through issues calmly, he treated it as a war. He would throw things near me in rage, turn arguments around until I was apologizing for my own hurt feelings, and coerce me into intimacy just so he would stop bugging me and we could be "normal."
Then, the red flags turned into horrifying revelations:

1. The Necro Confession: During a conversation where I half-jokingly called him out for predatory behavior, he casually confessed to searching for fake necrophilia content. My instinct told me to run, but my bad habit of trying to "fix" dangerous people kept me stuck.
2. The Betrayal and the Arrest: Months later, I ended up hooking up with his best friend ("Tyler"). Mark manipulated me into confessing, played it unnaturally "cool" in front of our other friend ("Ashley"), and then started playing mind games—going back and forth between being buddy-buddy with Tyler and telling us both to go kill ourselves. Shortly after, the police randomly showed up and arrested Tyler on a warrant. I strongly suspect Mark called them in.
3. The Snapchat Incident: A couple of weeks ago, I caught him Snapchatting an account belonging to a young girl. I called the police to report his predatory behavior, but they refused to even write a report.
   Knowing the police wouldn't act, I knew I had to look closer to protect myself. I managed to check his browser history and hidden folders on his phone. What I found made my stomach drop:
   Searches on Control: Multiple detailed searches asking how to remain in power over someone who is "defiant" and how to "punish them so they learn their place."
   Obsession with the Brain: Over 10 searches back-to-back asking "what is the sexual part of the brain?" alongside saved headshots of women where he had drawn circles and arrows pointing to the frontal cortex with question marks.
   The Graphic Images: An image of a human brain split in half with female genitalia edited into the center.
   The second I saw those images, a chilling memory hit me: months ago, he had "jokingly" told me that he wanted to cut my head off, leave the body, and take it for his pleasure.
   I realized in an instant that I wasn't just dealing with a difficult neighbor or someone struggling with mental illness. I was living next door to a violent, sexually sadistic predator who had been actively researching how to break my mind and act out his darkest fantasies.
   I have completely cut contact, gone silent, and I am taking steps to disappear and secure my life, but the fear of what he is capable of—and what he might do to others or those around him—is overwhelming.