1935 Marshall Pass Runaway

An earlier post regarding air brake exhausts prompted me to again check the Aug. 6, 1935 runaway of engine 492 and train on Marshall Pass near Mears Junction. The report may be found on the DOT Website under special collections. I know I have mentioned this mishap before. Hopefully I won't rpeat myself too much.
Engineman Allen stated getting a series of short exhaust as the train started down a 3-plus percent grade 1,100 feet after Mears Junction. The train was Salida bound. Conductor Hallock indicated he obtained one long exhaust from the caboose brake valve. It appears that the train already reached the runaway speed so Hallock's emergency braking had little effect.
That the engineer obtained a series of short exhausts and the conductor one long exhaust would seem to indicate a blockage close to the locomotive.
The train started down from Marshall Pass Station with 29 loads, one empty, a dead locomotive (the report did not note the number) and the caboose. Several stops were made and cars set out in the 14 miles between Marshall Pass Station and Mears Junction. After setting out the first car and cars 9 through 14 for an Alamosa bound train to pick up at Mears Junction the train was recoupled and the air pumpted to 80 psi. A long exhaust was obtained in the brake test indicated continuity of the train line.
Thirteen tresspassers were on the train. Four were killed along with head brakeman Ed Boots. Probable cause was air brake tampering although, other than a wrecked train, nothing was found amiss.