On April 9, two nationalist leaders, Saifuddin Kitchlew and Dr Satyapal, were arrested by the British officials without any provocation except that they had addressed protest meetings, and taken to some unknown destination.  

• This caused resentment among the Indian protestors who came out in thousands on April 10 to show their solidarity with their leaders.  

• On Baisakhi day, a large crowd of people mostly from neighbouring villages, unaware of the prohibitory orders in the city, gathered in the Jallianwala Bagh, a popular place for public events, to celebrate the Baisakhi festival.  
• Local leaders had also called for a protest meeting at the venue. It is not clear how many in the 20,000 odd people collected there were political protestors, but the majority were those who had collected for the festival.  
• The troops surrounded the gathering under orders from General Dyer and blocked the only exit point and opened fire on the unarmed crowd. 
• No warning was issued; no instruction to disperse was given. An unarmed gathering of men, women and children was fired upon as they tried to flee. 

Source: Spectrum Modern India.