Sounds like you came up with your own Dynamic braking..... 
Caused by a "dynamiter" car Also know as a kicker, Sometimes but not always would cause a emergency brake application of the whole train . and also hard to find.
OK I've never worked a job with dynamic braking and never with out a caboose but what happens to the dynamic brakes in an emergency brake application. Do they cut out? Engine drops it's reverse load? and of course the engines brakes apply.
