The Date Was Advertised in the Gazette

A MURDER IS ANNOUNCED
and will take place on Friday, October 29th, at Little Paddocks, at 6:30 p.m. Friends please accept this, the only intimation.

Everyone thought it was a harmless game. And so on the night of October 29, the neighbors dropped by, just out of curiosity.
Then, as the clock chimed 6:30, the room went dark,
A gun exploded!
A body fell!
A woman screamed!
When the lights went on, a man was found lying on the floor. He was wrapped in a black cloak. He wore a black mask and he lay in a pool of blood-dead.
There had been thirteen people in the room-thirteen witnesses who might have identified the killer.
Who was the corpse?
Who was the killer?
And why had this murder been announced?