Several songs from come to mind about President Kennedy' death. These include:

"Abraham Martin & John" pop song popularized by Dion definitely doesn't have the lyrics you are looking for

"That Was The President" by Phil Ochs also does not have your line

Two others that I don't have printed versions and haven't listened to for a long time:

"Special Friend" by John Stewart recorded by Kingston Trio (Time To Think, and Capitol Years)

"Summer of His Years" recorded by Chad Mitchell Trio (Reflecting)

rich r