Columbia University professor harassment

My name is Sawyer Allen, I am a 29-year-old trans man working in a frame shop/ design center. There I was approached by . He came with his mother looking to get his artwork framed. I performed my duties respectfully and with exemplary customer service. I thought nothing of it at the time, but unbeknownst to me this would be the start of what I could only call a nightmare. The next day he found me on Instagram (which I did not provide him with as I do not use my work to forge relationships.) He started to message me about his order, which is not the method or place to do so. My Instagram is not a part of customer services, he'd also ask about the times and dates that I'd be working at that location in a way that hinted that he was aware of me working at multiple locations. He'd visit regularly and ask for me in particular when I was not there. This made me uncomfortable, but I still had no idea how far he would go. During our last interaction in the store, he was banned from the store and stated he would "see me later." Once that happened, he started to message me on my Instagram non-stop. I blocked his account and at least three other alt accounts however, this only egged him on more to continue to message and harass me. He made it clear he was watching my every move. While I blocked his main account before I thought to screenshot, below I will provide messages from his alternative accounts showing him harassing and threatening me. At this point, I am unable to leave my house as I fear whatever he has planned for me. I have missed many days of work because of this and my mental health has taken a dive. When I sought legal help he mocked me for doing so and claimed that there was no way I could protect myself from him and that I'd eventually regret my attempts to avoid and ignore him. I have messages of other victims claiming that this is his M.O. and I hope that you will take steps to help stop this from continuing.Due to feeling unsafe to leave my house, it has taken a huge toll on me finically! & I was already in a horrible finical bind. I am begging for any form of help. Please, I just want to live my life in peace