Transcript for Hotel Room 225's Killer Finally Exposed
Reporter: Room 225 at the best western in the tourist town of boone, north carolina. One room, in just two months, three deaths. Elderly male, elderly female. Neither one is breathing. Have cpr in progress. Reporter: First, it was daryl and shirley jenkins, found dead in room 225. Is anyone there willing to attempt cpr? They're doing it right now. They are doing cpr right now? Been doing it since we found them. Okay. Four people working on them and there's no response. Reporter: That was APRIL 16th. Three days later, the solinski family throws a birthday pool party and sleepover at the hotel for their daughter levi and eight friends. They check into room 325. No one tells them about the jenkins tragedy in the room just below, and soon enough they have a disaster of their own. All girls were very sick -- puking in bathtubs, sinks, toilets -- while I'm calling their parents. They were falling off like flies, and it was pretty scary. It was just supposed to be fun. And then, it turned to dangerous. Reporter: Solinski says she complained to the front desk. I told them again in the morning, "there is an environmental hazard in this room. You need to get somebody in here." Nobody ever said, "well, actually, last week, this happened below you." My name was written on a yellow sticky note, and I was told the general manager would be told. Reporter: But damon mallatere, whose company managed the hotel, swears the clerk never told him. So you were not informed by your employees that people had gotten sick in the room right above 225? I was not. Reporter: And then, even though the medical examiner had not yet determined what killed the jenkins, six weeks later mallatere reopened room 225. You thought there was no reason to be suspicious of something inside the room? We never would've reopened that room if we had any thoughts whatsoever that there was something wrong or that that would hurt somebody. Reporter: The death trap was ready for its next victims. Jeannie williams and her 11-year-old son, jeffrey. I think he was laying on the covers. Just like he had went to sleep. Reporter: In his pajamas? Yes. Reporter: Somehow, jeannie survived. She's not talking, right? Reporter: She's unconscious? She's unconscious, but she is alive. Reporter: But this time an alert 911 operator realizes the deadly danger is right there in room 225. Okay, I'm going to need you to just to go ahead and get out of that room. Okay, get out of the room. Everybody get out of the room. Get out of the room. Reporter: First responders arrive. Their hazmat detectors go crazy. They follow a toxic trail downstairs, past the pool and at last corner the killer, a faulty pool heater, which generates carbon monoxide, an odorless, invisible and deadly gas. The heaters exhaust pipe was supposed so conduct the carbon monoxide safely outside. But hidden under a drop ceiling, right under room 225, state investigators find the pipe is busted, full of holes propped up with a vhs cassette tape and a hotel ice bucket. Spewing poison gas into the room above. Mallatere, the manager, says he knew nothing of these problems. Why wasn't the killer in room 225 stopped before jeffrey williams died? The police investigation and "20/20" reporting shows he died of a tragedy of errors. Attorney chad poteat says soon after the jenkins were killed, their family warned the best western that they suspected carbon monoxide was to blame. That was before jeffrey died. So they were warned before jeffrey died that there could be a carbon monoxide problem -- absolutely. Reporter: -- By the family of people who had just been killed in that same room, and they didn't do anything about it. Apparently, if they did, it wasn't enough. Reporter: The hotel manager says authorities never mentioned carbon monoxide. Do you feel any responsibility for what happened? I don't believe that anybody in any way involved, whether it be the authorities or the contractors or my employees or myself, should go to bed tonight and not feel responsibility. Reporter: But what you're saying is that doesn't mean you're criminally culpable? I would never willfully hurt a guest if I knew that I could keep that from happening. Reporter: The most outrageous failure of all, the state tells "20/20," it sent shirley jenkins' toxicology report, showing she'd been killed by carbon monoxide, to medical examiner brent hall on june 3rd in plenty of time to save a little boy's life. Jeffrey williams would not check in for another four days, but not a peep from dr. Brent hall, not a single warning. Is it possible that, had the medical examiner who had the report, the autopsy saying that it was carbon monoxide poisoning that had killed the jenkins in the same room in which jeffrey williams was staying, and he had delivered that report to the hotel or the police, jeffrey might still be alive? I absolutely agree with that. Reporter: We went to dr. Hall's office, where a receptionist was unreceptive. Hi, there. Can I help you? Reporter: I'm matt gutman with abc news. Can we talk to you? I'm not interested! Reporter: Hall has resigned as the medical examiner. This isn't the first time carbon monoxide has killed in a hotel. Dr. Lindell weaver has been warning about the danger for years. The reason a hotel is particularly dangerous is really because of the sheer number of people who could be there. Reporter: Weaver studied carbon monoxide incidents in motels, hotels, and resorts in one five-year period, more than 750 people were poisoned. Like the group of five boys celebrating a birthday in a miami hotel, all of them killed. It's exkeyedly dangerous. Reporter: Unlike smoke detectors, there is no federal requirement for carbon monoxide detectors in hotel rooms. A handful of states, now including north carolina, do require them in some areas of the hotel. Jeffrey williams' family is starting a foundation to raise awareness. And it's very simple. Carbon monoxide detectors are cheap in the grand scheme of life. Reporter: Last week, a grand jury handed up indictments in the case. Three counts of involuntary manslaughter and aggravated assault, for jeannie williams injuries. The d.A.'S office decided to submit to the grand jury, one name, and that name being barry damon mallatere. Reporter: Mallatere says his legal troubles don't compare to what the families of the victims have gone through. How often do you think about this? Every day. Reporter: That boy, that elderly couple? Every day. I need to cut. Reporter: Heartbreaking. All that sweet blue ridge mountain air right outside the window. And inside room 225, people literally dying for a breath of fresh air. Amidst all that grief, the williams can't seem to catch theirs. Jeannie williams was reminded of what she's lost at a recent wedding. When it came time for the mother and the groom dance, i won't have that. I won't have the mother and the groom dance. But I just take it one step at a time, and I just know I'll see him and I'll dance with him in heaven one day.
This transcript has been automatically generated and may not be 100% accurate.