Abdul Kalam, who was India's president from 2002 to 2007, visited the European Parliament in Strasbourg, France, on April 25, 2007. (Christophe Karaba/EPA)

One of India's most popular presidents, Abdul Kalam, died Monday after he collapsed during a lecture to business management graduate students in the northeastern city of Shillong.

The 83-year-old Kalam, who was president from 2002 to 2007, was affectionately called the “missile man,” “scientist-patriot” and “people’s president” of India. Many Indians credited him with lending relevance to what is largely a ceremonial post.

Kalam suffered a cardiac arrest during the lecture and was declared dead as soon as he was brought to the hospital. He was in Shillong to deliver a lecture titled “Liveable Planet Earth,” according to his last tweet.

Kalam, a rocket engineer, played a key role in weaponizing India’s nuclear program and was instrumental in conducting the country’s second nuclear test, in 1998, which earned the wrath of the United States and was followed by international sanctions. He received several national awards for his work.

“As a president, his life, his work and everything about him continues to show the way for India. His life-long efforts to deploy scientific intellect in making India powerful is truly the nation’s wealth,”  Prime Minister Narendra Modi said in a televised address. “He used to say teaching was his passion, and he spent his last moments among the students doing what he loved most.”

During his term in the office, Kalam opened the imposing gates of the presidential palace and made it more accessible to ordinary Indians by hosting schoolchildren, farmers and scientists. He was the author of the best-selling inspirational book called “Ignited Minds — Unleashing the Power Within India,” which was very popular among schoolchildren. He was the visiting professor to many management, science and technology colleges across India.

His quotes were often printed on post cards, calendars and greeting cards.

“India has today lost one of its most inspirational persons. Dr. Kalam was not merely the president but he was to every Indian a role model and an ideal citizen,” said Arun Jaitley, the finance minister. “Everything about him was positive. He thought well, he had positive ideas. His contribution as a scientist, his contribution as a president was unparalleled. He has left a void for all of us.”

Here is a sample of how Indians remembered Kalam on Twitter:

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