PLAISTOW — The three people who died of carbon monoxide poisoning all worked for the same company, and had just returned from a weekend convention, a coworker said.
Frank Licata of Andover, Mass., said Kirk Walsh, 32, worked as the regional director for ACN Inc., a direct seller of telecommunications services.
The State Medical Examiner's Office identified the dead as Walsh, 32, Maryanne Comparato, 47, and John Adams Jr., 28. All three victims died as a result of accidental carbon monoxide poisoning, the medical examiner's release said.
A fourth man, identified as Keith Small, was discovered alive and is in critical condition at Massachusetts General Hospital, officials said.
Walsh owned the home at 5 Center Circle where two men and a woman were found dead in their beds Tuesday morning. A third man was discovered alive and is in critical condition at Massachusetts General Hospital, Fire Chief John McArdle said.
Licata said he worked with Walsh and the three others who had stayed at Walsh's house Sunday night. He said the four had just returned from an ACN convention in North Carolina.
Friends and co-workers spent Monday trying to reach Walsh and the others, he said.
"When all four of them didn't return calls, people got very suspicious and that's when they called police," Licata said.
Walsh's car, with "ACN" on his license plate, sat snow-covered in his driveway Wednesday.
McArdle said Walsh's home had a carbon monoxide detector, but the batteries had been removed.
The deaths have prompted warnings about the dangers of odorless carbon monoxide and the importance of having working detectors.
"The first thing I did was check my detectors and I've been passing the word around. The folks at work, I told them to make sure they go home and check them. Do yourself a favor. Do everybody a favor," said neighbor Raymond McKay.
McKay said he would sometimes help Walsh clean snow from the driveway; last Thursday while clearing snow Walsh told him that he was going away on business.
"He helped me a couple of times and I helped him. Just neighborly things. He was a busy guy. He was in and out all the time," he said.
McKay said Walsh has owned the house for several years.
Authorities are trying to determine whether the heating system in the basement was operating properly and installed correctly.
"It was the only source of carbon monoxide in the building," McArdle said. "We're pretty sure from what we've seen that that would be the source."
Town Manager Sean Fitzgerald said the deaths have stunned the community.
"Plaistow is a tight-knit community," he said. "It's a community with people who care about our neighbors. It will certainly be a tough loss for us, but it's certainly a painful reminder that there are simple steps people can take to help ensure that they're safe," he said.