Father-of-three Mr McCullough, train conductor Donald Dinnie, 58, and passenger Christopher Stuchbury, 62, died when the 6.38am service derailed near Stonehaven, Aberdeenshire, after hitting a landslide. Injured off-duty rail worker Nicola Whyte crawled from the wreckage and walked three miles to raise the alarm because there was no mobile phone signal in the area.
Miss McCullough wrote on Facebook yesterday: “To ScotRail, we are still waiting on answers.
“I am holding you responsible for my brother’s death unless we are advised otherwise.
“During one of the worst storms to hit Scotland you sent my brother out to drive a beast of a train.
“I wish Brett had refused but that wasn’t in his nature, he would never let anyone down.”
Initial findings of the Rail Accident Investigation Branch show that after passing Stonehaven the train was stopped at Carmont and the signaller sent a radio warning about a landslip further south.
Mr McCullough was instructed to turn back towards Aberdeen but had travelled around 1.4 miles when the train, made up of two engines and four carriages, hit a landslip and derailed.
His sister said that it “ultimately led him to his death in the most horrific way”.
She told ScotRail: “Why wasn’t he instructed to remain in place until help arrived? You need to come up with an honest answer.
“I don’t know who is responsible for those decisions yet, I’m sure you are being protected. But you’ll not be able to hide out for ever.
“We will be taking you down, it’s just a matter of time.”
ScotRail managing director Alex Hynes said railways would hold a one-minute silence on Wednesday, adding: “Our hearts remain broken and will do for a long time.”
