A health alert warning residents of northern Michigan's Kent County that "possibly hundreds of people have been exposed to HIV" was issued Tuesday after the arrest of David Dean Smith, a 51-year-old HIV-positive man who told police he was on a mission to infect as many people as possible, MSNBC reports. Smith allegedly told Grand Rapids police last week that over the past three years, he had engaged in unprotected sex with as many partners as he could -- a number he estimated to be in the "thousands" -- in an effort to infect them with HIV and kill them. Police arrested Smith Friday on sexual offense charges and he is currently in Kent County Jail in lieu of $100,000 bond with preliminary hearings scheduled for Jan. 4 and Jan. 9. When asked to comment on the case, Smith's attorney Richard E. Zambon told MSBNC that he is "concerned about his mental health" and is planning on "exploring all options" for defending Smith. According to documents filed with Grand Rapids 61st District Court, Smith targeted Michigan residents as well as those living many states away, whom he contacted via Yahoo! Personals. That was the method Smith used to contact one of the two victims that have already come forward. This woman agreed to be interviewed by Grand Rapids news station WOOD-TV on the condition of anonymity, telling reporters that she contracted HIV in 2008 and knew immediately that Smith was the person who had infected her. Right before his arrest, she said, he allegedly sent her a text message that read "Turning myself into the law, my life is over. Take care. Always love you." It's unclear why Smith chose to alert authorities of his behavior at this time, but court documents suggest he has a history of mental illness which includes a recent admission to Pine Rest Christian Mental Health Services for threatening suicide. According to Michigan Live, hospital records say that Smith is "sexually aroused by causing pain to females." How many people Smith directly infected over the past three years is difficult to determine, but the victim who spoke to WOOD-TV said Smith claimed to have had sex with as many as 3,000 people of both genders. The Kent County Health Department is encouraging anyone who believes they may have been infected by Smith to come forward. Anyone concerned that they may have been infected can call the Kent County Health Department Personal Health Services Clinic at 616.632.7171. All calls and HIV testing is confidential.