I want to know which avenue to pursue. I currently have a problem with a Co-worker that has been tagging (l writing, carving, scratching etc.) on everything and anything he can in my work area and the restroom stalls and walls about me. He tags calling me

Its been going on for months now. I believe that it would fall under sexual harassment. I work for an industrial plant as a steelworker with nothing but men. I have an ex-coworker that was fixated on me from a different shift and different work area. Several months ago. He begin to leave derogatory, sexually based references throughout my work area by tagging (writing, carving, scratching etc.) everywhere and on everything he could. It was remarkable I might add as to the amount of messages he was leaving. Almost as if he would write these messages all night long during his 10 hour shift. He would tag messages for and directed to me that were very explicit. Like, how he liked me sexually and the things he wanted to do with me etc. He was also leaving his name in all of these areas as well. That's one of the reasons how I knew who was leaving these messages. As I confronted him about it, he became very angry and stated that it wasn't him. Days following this, the messages turned to name calling and accusations of me being gay. He begin to make these messages more noticeable for others to read. He started tagging other areas of the plant this time, like the restroom stalls. He begin to tell other employee's on his shift that I was gay and who knows what else.I confronted him again about it, but this time I let him know that I was very angry and that I would report him and pursue discipline through the company if he didn't stop and didn't remove everything he had tagged. Soon after he removed them, oddly new messages returned and asking me to meet him in different places outside of work. He eventually quit working for the company and left. Soon after, one of his buddies from his shift was transferred to my shift. This guy asked me what had gone on with him. After a few days he became angry with me stating that I had wrote a note to him calling him "Daddy". The note he mentions is a sticky note I had attached to a sledge hammer I had repaired for him. Earlier the morning he and I had a conversation about a stencil he had made. It was from a sticker of a dragon with wings and a tiny little crown on top all inside a circle. I told him the crown was not really distinguishable and that I would draw him a better one. So the sticky note was attached to his sledge hammer I took back to him which had the crown I drew with an arrow pointing to it with "Like This" I wrote above it. underneath the crown, I wrote, " This belongs to (his name) and the area/dept. he works in. When I went to give it to him, he already had an angry look on his face. I walked up to him and told him while holding the hammer up, telling him that I wanted to engrave the crown on the handle with the words "King Daddy". Meaning that we were giving his sledge hammer a name. He misunderstood I believe , thinking that I called him "Daddy". Supposedly he was enraged and sent his partner to tell the Union President about it. 10 minutes later his partner and the Union President came to talk to me asking me what I had done to upset him. I explained and they told me to no longer discuss anything personal and to remain professional with him. I agreed and they left. The next day he begin tagging my work area and the restroom. Writing my name saying that I was gay and a fag. The next day I noticed that the only new words he tagged was " Karma" & "Death". The very next day I found one bug message carved into a steel metal plate "I hate Gays, Fags, Bisexuals & a LGBT Peope". He stated that he really really hated them so bad that he would burn them all to ashes. He then writes "I know your one of them and I hate you hate you hate you. You need to watch and fear me. When you're alone I will hunt and catch you and kill you. I won't be the one who does it, an animal wil". I've only mentioned this to 2 very close friends I trust and I have not communicated with him what so ever about anything he's tagged. I've seen him during our shift and he stares and glares at me in passing. What avenue should I pursue best?