A brief argument lasting barely 90 seconds inside a moving local train ended in the death of a 31-year-old mathematics professor at Malad railway station on Saturday evening.

The victim, Alok Kumar Singh, was stabbed in the abdomen following a minor dispute over space inside a crowded compartment, railway police said. The accused has been identified as Omkar Shinde, 27, who works with his father at a diamond-manufacturing company in Marine Lines.