Police said he wore a brown knitted beanie hat, black framed glasses, a black double-breasted wool peacoat, beige chino trousers, dark grey gloves, light grey scarf, black shoes and black rucksack.
Detective Inspector Ian Wright said: "This is a particularly shocking incident and I'd like to express our sincere condolences to Dorothy's family who are being supported by officers, and ask that their privacy is respected at this incredibly difficult time.
Dorothy's family released a poignant tribute, via the police force, in which they say the "lively and outgoing" pensioner is sorely missed.
Now, British Transport Police said officers are still keen to speak with a man who witnessed the incident.
"The investigation into this incident is ongoing, and I would continue to urge anyone who witnessed the incident, including the man mentioned, to come forward and assist our inquiries.
