By Erich Wagner (File photo)

Police revealed Thursday that a similar weapon was used in all three of the city’s most prominent unsolved homicides and they are now investigating them as a “series of cases.”

Chief Earl Cook said at a press conference that police received the ballistics report studying bullet fragments found in the Ruthanne Lodato case, which confirmed that the fragments exhibit the same general rifling characteristics of a small-caliber gun to those found in the killings of Ronald Kirby in November and Nancy Dunning more than a decade ago. But microscopic analysis was inconclusive, meaning police could not confirm if the same gun was used in all three homicides.

“We compared all three and the lab said it was the same class of rifling, but they cannot determine that a single weapon was involved,” Cook said. “Now we are looking at it as if all three are linked.”

But Cook still left the door open to the possibility that the homicides were separate incidents, citing the commonness of the class of weapon used in the shootings.

“We could — and I’m speculating now, I hate to say it — probably a million of this type of gun in homes in the U.S.,” he said. “And that’s probably a low number.”

He also noted that, at least in the Lodato case, investigators were dealing with fragments of bullets, making it difficult to ascertain exactly what caliber gun was used.

“We have fragments here, not whole bullets,” Cook said. “They’re not intact.”

Cook reiterated his call for residents to remain vigilant, both for their own safety and to report sightings of men who match the composite sketch of the suspect — an older white man with a gray beard.

“We want everyone to have a heightened sense of awareness,” he said. “Look before you open your door; know who you’re talking to; know who is visiting your home.”

Cook said while the ballistics report is helpful, the inconclusiveness of its results means police still cannot rule any possibility out.

“We don’t eliminate anyone as a suspect until we have an arrest,” Cook said. “We can’t rule anything out until we narrow it down to one person.”