APJ Abdul Kalam -- former president of India, eminent scientist and a role model for the country's youth -- died Monday at the age of 83. Kalam, who served as the country's president from 2002 until 2007, was fondly known as the “missile man,” for his role in developing the country's defense and nuclear technologies.

Kalam collapsed while addressing students at the Indian Institute of Management in Shillong, capital of the northeastern state of Meghalaya. According to local reports, Kalam suffered a cardiac arrest and was declared dead after doctors failed to revive him. Kalam’s body will be flown to New Delhi on Tuesday for burial.

“Kalam would be long remembered for his passion for science and innovation and his contribution as an eminent scientist, administrator, educationist and writer," President Pranab Mukherjee reportedly said.

Before becoming president, Kalam was a scientist and administrator for four decades, mainly at the state-run Defense Research and Development Organization and the Indian Space Research Organization. During his stint there, Kalam was credited with helping to develop the country’s first indigenous satellite-launch vehicle, and played a crucial role when India tested its nuclear weapons in 1998. 

“We must think and act like a nation of a billion people, and not like that of a million people,” Kalam reportedly said, at the time. “Dream, dream, dream! Conduct these dreams into thought, and then transform them into action.”

After his presidential term ended, Kalam traveled across the country to speak at schools and colleges, encouraging and inspiring an entire generation of students to follow their dreams.

India's Prime Minister Narendra Modi took to his Twitter account to remember Kalam.

Kalam, India's eleventh president, was born Avul Pakir Jainulabdeen Abdul Kalam in 1931 into a middle-class family in Rameshwaram, a town in the southern Indian state of Tamil Nadu. 

He studied aeronautical engineering at the Madras Institute of Technology, and was proud of his Indian education and often described himself as "Made in India," having never trained abroad.

He wrote several books, including the autobiography “Wings of Fire” and “Ignited Minds: Unleashing the Power Within India.” He was honored with several awards, including the Bharat Ratna, India’s highest civilian honor.

Several Indian politicians and celebrities also took to their Twitter accounts on Monday to mourn Kalam's death, including former finance minister P. Chidambaram, Home Minister Rajnath Singh, Academy Award-winning music composer A.R. Rahman and Bollywood superstar Amitabh Bachchan.