On the morning of 31 October 1984, his mother was assassinated by one of her bodyguards; later that day, Gandhi was appointed prime minister. His leadership was tested over the next few days as organised mobs of Congress supporters rioted against the Sikh community, resulting in anti-Sikh massacres in Delhi. Sources estimate the number of Sikh deaths at about 8,000–17,000. That December, Congress party won the largest Lok Sabha majority to date, 411 seats out of 542. Rajiv Gandhi's period in office was mired in controversies; perhaps the greatest crises were the Bhopal disaster, Bofors scandal and "Mohd. Ahmed Khan v. Shah Bano Begum". In 1988, he reversed the coup in Maldives, antagonising militant Tamil groups such as PLOTE, intervening and then sending peacekeeping troops to Sri Lanka in 1987, leading to open conflict with the Liberation Tigers of Tamil Eelam (LTTE). In mid-1987, the Bofors scandal damaged his corruption-free image and resulted in a major defeat for his party in the 1989 election.