When the coroner, Dr. Richard Jorgensen, arrived a few hours later, he was struck by the seeming normalcy of the Stack residence. ‘‘This could be my suburban family home,’’ he told me months later. ‘‘This was a home where people who cared about their family lived.’’ Jorgensen said he could tell just from looking at Joan that she had been very ill. ‘‘I can’t imagine the burden of this family for these 50-some years,’’ he said. ‘‘I’ve heard people judge Frank in a critical way, and I think this is truly ‘Walk a mile in their moccasins before you say anything,’ because I’ve been through the house and talked to the various members of the family, and this isn’t a situation where there was anything other than love that I saw all around this place.’’

Frank Stack was a big man — 6-foot-1 and 240 pounds at the time of the shootings — and a big presence. He was a Korean War veteran, a retired Commonwealth Edison lineman, an ardent Green Bay Packers fan on a Chicago Bears block. Neighbors describe him as a kind of patriarch, the first guy they met when they moved in, always willing to lend a hand, dropping off a coffeecake he had picked up for you at the farmers’ market because he knew you were having a hard time. His neighbors acknowledge that he could be stubborn and a bit quick to lose his temper, but many viewed that as part of his charm. Joan was smaller, quieter, deeply Catholic, a ‘‘saint’’ in the eyes of those same neighbors. She kept an impeccable home, had dinner on the table every night, and always asked you how you and your family were doing, never complaining about her own lot even as she grew increasingly sick.

As Stack had gotten older, he couldn’t get around the way he used to. Bill Mueller, a friend who lived across the street for nearly 32 years, quietly began to help out with work around the house. He watched from up close as both Frank and Joan started to decline, with Joan becoming completely dependent on others because of her ill health. According to neighbors, Frank had undergone several operations for severe sciatica, but the pain had become increasingly debilitating. He and Mueller talked about putting in an electric lift to help with the stairs, but they never got around to it.

Though Stack was devoted to all of his children, he had a special bond with his only son. He saw Frankie at least once a week, taking him out for rides in the car, bringing him home for dinner or delivering a cake to the group home for him to enjoy with the staff and other residents. Frankie loved chocolate and he loved to be outside, listening to a lawn mower or taking a flower and twirling it in his fingers. He was less social than his sister, preferring to watch what everybody else was doing before deciding whether he wanted to join in himself.

Stack rode the staff hard at the Ray Graham Association, the organization that oversaw the group homes where Frankie and Mary lived, and he was particularly hard on the people who looked after Frankie. When Frankie’s eyesight grew progressively worse and a doctor discovered a detached retina, Stack became convinced that a housemate had been hitting his son in the head, despite assurance from the staff at Ray Graham that no such thing had occurred. ‘‘Frank had a side you didn’t want to get on,’’ Jane Mueller, Bill’s wife, says. ‘‘I’m sure he gave Ray Graham an earful. Frank was never happy. It was never good enough.’’ After Frankie’s eye surgery, Stack became upset that there wasn’t enough light in the living room of the group home to allow his son to recover properly.

‘‘They had very high expectations for us, and that was O.K.,’’ Kim Zoeller, the head of the Ray Graham Association, told me when I visited her at Ray Graham headquarters in nearby Lisle. She has worked for the association in various roles since 1994, and she knew the Stacks long before Frankie and Mary went into group homes. ‘‘We definitely saw a little bit — a side of Mr. Stack, when he had concerns, all from a passion for his kids,’’ she said. ‘‘He wanted us to make sure that we knew that whatever this issue is, you need to tend to it. And we wanted to know.’’