It was Parallax's influence that was responsible for Jordan's subsequent murderous activity. When Jordan destroyed the Central Power Battery, he unknowingly freed Parallax, which grafted itself onto his soul, and suppressed Ganthet's memories of the parasite.
Parallax's influence is the cause of Jordan's violent actions, leading to him destroying the Central Power Battery and releasing Parallax into his soul. This resulted in a parasitic relationship between Jordan and Parallax, erasing Ganthet's memory of the parasite.