A quiet upstate New York community has been shaken by a nightmare discovery after police say a grandmother is suspected in the deaths of her daughter, four young grandchildren and herself inside their apartment building.

Police in Mechanicville, New York, said officers found the bodies Tuesday after worried neighbors reported they had not seen the family for several days.

The grandmother was identified as 64-year-old Amy Steadman. Police said the victims were her daughter, Sarah Myers, 44, and Myers’ four children: Harper Harmon, 13, Hudson Harmon, 11, Gavin Harmon, 10, and Gracelynn Harmon, 10.

Now, investigators say the case appears to point to an unthinkable family tragedy.

Mechanicville Police Chief William Rabbitt told reporters Thursday that evidence found inside the apartment suggests Steadman may have been involved in the deaths.

Investigators recovered what Rabbitt described as evidence “to indicate intentional poisoning,” including numerous prescription and over-the-counter medications. He also said police found a handwritten note and other circumstantial evidence that “strongly suggests” Steadman was involved.

The chief said there was no evidence that anyone from outside the home was responsible.

Toxicology testing is still underway, and officials have not released a final cause of death for all six people. However, Rabbitt revealed one especially chilling detail: one of the children suffered fatal sharp force injuries.

Authorities have not publicly revealed a motive.

Police said Steadman, Myers and the children all lived in the same apartment complex in Mechanicville, a small city located about 18 miles north of Albany.

The children’s father lives in Utah, according to the police chief.

The investigation remains ongoing as the devastated community waits for more answers in a case that has left neighbors horrified.