On 13th April 1919 (exactly 100 years ago), General Reginald Dyer gave firing order in Jallianwala Bagh. He was known as “The Butcher of Amritsar” for this heinous massacre.
In 1940 he was assassinated in London by Udham Singh
For those who can read Hindi, here is a good blog about the massacre.
For English readers: here is Wikipedia link