No charges have been filed yet in connection with the killings. Friends of the McCullough family say the police are questioning a relative of the victims at Area One Police Headquarters.
Police have continued to question that relative ever since he was taken into custody Tuesday night.
That person of interest was discovered living in a neighbor's basement. Angela Scott showed ABC7 the door to a crawlspace right off the basement of her family's Englewood home. Tuesday night her 17-year-old brother was alone in the house when he heard a voice coming from the crawlspace.
"My brother called me around 8 p.m. and told me that there was an intruder in the basement. As he was calling me, on the phone talking to me, I told him to unlock the door. When he unlocked the door, the man was discovered there," said Scott.
The man fled and ran down the 6100-block of South Hermitage naked. Neighbors found him inside the home where three people were killed April 4.
Allen and Dana McCullough and their 19-year-old son were shot to death. Police have been looking for a relative neighbors say is the man police took into custody Tuesday night.
"I'm hoping that's the person, because it's a great loss, because they were a great family, they had jobs, they worked. They had a good family," said Jesse Ingram, friend of victims.
Allen McCullough was a Markham Park Police officer. His wife was a postal worker. Neighbors say the man police are questioning lived with the McCulloughs and had not been seen since the murders. The Scotts have no idea how long he had been living in their crawl space.
"It was scary but it's good he's caught," said Angela Scott.
The Scotts discovered an empty jar of peanut butter and a blanket in the crawlspace. Besides not knowing how long he was there, Angela Scott is surprised he was able to get in.
"There's a wooden piece that was cut there and he went through there and went somehow through our back door, which I always bolted and locked. Somehow this was cut open, too," Scott said.
It is unknown how long the man was living in the Scotts' house, but neighbors believe he had been living somewhere on the street since the murders. The McCulloughs happen to live right across the street from a elementary school.
Police continue to question the man. So far charges are not filed.