RPM, who calls herself a "targeted individual" and has a website devoted to those claims, said May reached out to her through Facebook about a week ago in anguish.
"He told me he just didn't want to go on living like this," Mitchell said. She said that after their initial conversations, she became wary of May, concerned that he might be what she called an "impostor." May continued to try to contact her and left three voicemails between 9:19 p.m. and 9:42 p.m. ET Wednesday, she said.
"I am currently being cooked in my chair. I devised a scheme where I was going to expose this once and for all and I really need you," he said in one of the messages, which was provided to NBC News and authenticated by a relative as May's voice. "I do not want to die in vain."
In an email he sent at 11:19 p.m., he wrote: "I've been getting hit with the direct energy weapon in my chest all evening. It hurts really bad right now." Police say he opened fire on campus about an hour later.
