Complex sentence: The subsequent police brutality unleashed upon the unarmed students in the early hours of September 17,2014 triggered a wave of protests by students and teachers not only in Kolkata, but across the country in cities like Delhi, Mumbai, Hyderabad and Bengaluru.
Split into simpler sentences: The subsequent police brutality unleashed upon the students in the early hours of September 17 triggered a wave of protests by students and teachers. Demonstrations showing solidarity with the students started to take place in Kolkata and across the country in cities like Delhi, Mumbai, Hyderabad and Bengaluru.