My great uncle, or great-great uncle, was involved in the telegraph system then, just south of Buffalo. He was one of the first people who knew about this, quite a while before it was announced to the public.
There is a big house on Delaware Ave on the northwest side of downtown Buffalo where they swore in Teddy Roosevelt.
My best friend lived in an apartment just down the street when he was going to college.
Also in the neighborhood was IMHO the best looking Frank Lloyd Wright house other than Falling Water in the country.
I believe it took McKinley more than a week to die. TR was to attend a speaking engagement in New York and was then to explore parts of the state. He was informed that the President had been shot but would live. Owing to lousy medical care that did not happen. When the President took a turn for the worse, TR rushed to his side, but arrived too late.
This is the house in Buffalo I was trying to recall.
The Martin House is now a museum.