The assassination of Indira Gandhi was motivated by Operation Blue Star, an attack on Sikh separatists holed up in Golden Temple complex in Amritsar, India. Satwant Singh and Beant Singh fired thirty three bullets into Indira Gandhi's chest and abdomen. Initially Beant Singh drew a .38 revolver and fired three shots into Indira Gandhi's abdomen. As she fell to the ground, Satwant Singh fired all 30 rounds from his Sten automatic weapon into her body
Beant Singh was killed by gunfire soon after the assassination after he and Satwant had surrendered. Satwant Singh was arrested and later sentenced to death along with conspirator Kehar Singh. The sentence was carried out on January 6, 1989. Satwant Singh was the last man to be hanged in Tihar Jail in Delhi
Satwant Singh's father Tarlok Singh was a farmer and he was born in the village of Agwan in Gurdaspur District, Punjab. His mother's name was Piar Kaur. His brother's name is Sarwan Singh Agwaan. He married Surinder Kaur (daughter of Mr. Virsa Singh) on May 2 1988 while he was in jail. His fiance married him in his absence by marrying his photo in an Anand Karaj.
Their acts brought their immediate families into limelight, resulting in their winning two Lok Sabha seats from state of Punjab. The Lok Sabha is a directly elected 552 member lower house of the Parliament of India. Late Prime Minister Indira Gandhi was also an elected member of the same house.
In the year 2004, his death anniversary was again observed at Akal Takhat, Amritsar, where his mother was honored by the head priest and tributes were paid to Satwant Singh and Kehar Singh by various political parties.
On January 6, 2008 the highest Sikh temporal seat (Akal Takhat, Amritsar) declared Satwant Singh and other assassins of former prime minister Indira Gandhi martyrs of Sikhism SGPC also paid homage to both Satwant Singh and Kehar Singh and called them "martyrs of Sikh nation". Shiromani Akali Dal observed their death anniversary as 'martyrdom' on October 31 2008
http://www.panthic.org/news/130/ARTICLE/3798/2008-01-10.html - Shaheed Satwant Singh