For starters: Here's the very first assassination song I found: It's by Fred Geis---Fred, if you're out there it'd be great to hear from you! TITLE" _THE LORD OF THE LAND_
The song was finished before Oswald was killed and the verse about Ruby shooting Oswald ("the slayer lies dead at his feet") was added a day or two later.

Where is the master of the house,
Where is the lord of the land,
He's gone to rest with his youngest son,
Gone to a far distant land.

Where is the wife of the lord of the land?
What of his kindred and keep?
His mourning wife sails on a bonny great ship,
Over the ocean and deep.

Where is the brother of the lord of the land?
What sins does he repent?
He lies and he cries in the arms of his love,
His sorrows his sins do all rent.

What of the people who live in the land?
What of the crofters and fens?
There's crying in the villages and weeping in the towns,
Lamenting can be heard in the glens.

Where is the slayer whose arrow did quick
To kill the lord of the land?
He lies in a cell and he ponders his fate,
He knows not what sprang from his hand.

The leaves on the trees are dying and dead,
The flowers are dead on the heath,
The lord of the land lies dead in his grave,
The slayer lies dead at his feet.

(Repeat first verse)

(This is a non-specific song of the killing of JFK. I taped Fred singing it in my coach house in Chicago's Old Town area a day or two after Lee Oswald was killed. It was the beginning of a search that has gone on for almost 40 years.----Art Thieme)