After the police investigation petered out, an architect and part-time paranormal investigator or "self-styled authority on poltergeists" as the Milwaukee Journal would have it, named John C. Parker took over. He said that he was "pretty sure poltergeists are to blame." He set up a recording thermometer near the bathroom window where three panes had been broken to prove that sudden drops in temperature showed evidence of ghosts. Not exactly the most balanced method of investigation to say the least.
The police did return to interview the 13 year old grandson and discovered "that he had been experimenting with a Christmas chemistry set". When told Parker added, "The only way that anyone could break a window with that set would be to throw the whole thing through the window." Touché!
After all the hoopla of the week of 39 broken panes and the story spreading nationally, Mrs. Papineau did not experience anymore disturbances, or at the very least, she never reported them. As for a cause of the phenomenon, one could pull any number of explanations from their proverbial butt: chemistry sets, trucks going by, small localized earthquakes, some acoustic phenomenon of local origin, some kind of localized atmospheric pressure inversion (okay that one doesn't make sense). At this point a poltergeist explanation is as good as any other.
The case remains a mystery.
Milwaukee Journal - January 15, 1959
Daytona Beach Morning Journal - January 15, 1959
Binghamton Press - January 16, 1959