Just to summarize what the user + is writing in german:
The perpetrator seems to be a Phillip Fusz, 35. At some point this man with an evangelical upbringing and academic and professional background in finance joined the JWs. He lost his financial business during the pandemic and found solace in the Bible (his theology seems clearly influenced by the JW worldview). In December 2022 he self-published a book on Amazon with his theological views, titled "The Truth About God, Jesus Christ and Satan". In the beginning of March 2023 he faced a Judicial Hearing and was disfellowshipped (for apostasy, I presume).
Taken from the synopsis: "This book is a standard reference when it comes to Theology & Law. This book is a must read for all persons who hold a function or leading position in the fields of economy, science, politics and entertainment, and also for all religious persons." Seems like a deeply disturbed individual with a oversized notion of his self.