Jayco was a child born with parents. Days after his birth, they were mistaken as normal animals while they went off hunting for food. Jayco isn't his actual name, as he had two names in the past. The one the parents gave him was Sliske, but he was too young to remember that. The babe grew hungry and started crying, which caught the attention of a chief and his huntsmen in the rundown cabin where Jayco/Sliske was in. Taking in the babe, raising and calling him Riskel, since they didn't know his birth name. The chief had a biological son (the oldest) and said son grew attached to Jayco. A war happened between his clan and another, and the war was brutal, with many dying on both sides.
While he, his brother, and what remained of their army were stranded in the middle of nowhere. Jayco's vampire instincts kicked in, and he accidentally ate all of them, even his older brother. Well, all of them, except one, escaped and wandered their way back to the clan to tell the chief what happened. Out of agony and anger, he captured and held Riskel prisoner in a makeshift dungeon. To make matters worse, he throws his dead son's glass coffin (for him to see what he had done) in there as punishment for Riskel. The chief not having the heart to kill him as he still views Riskel as his son. As the years go on, he didn't die (he couldn't die) and kept talking to his brother to keep him sain throughout the years. Over time, he started acting like a wild animal as the hunger was getting strong to overcome. He feasted on rats to sustain him, but that didn't help as much.
His muttering became nothing, and the man only communicated as an animal would. Barking, howling, snarling, etc. Until Vivienne and Bella came and rescued him. He learned to talk again, with him giving the name Jayco as mentioning his old name traumatizes him, but he still is terrible when it comes to socializing with others.