The Head of the Mormon Church, Thomas Spencer Monson, has died at 90, the Church said on Wednesday. His death has thrown the about 16 million faithful into mourning.

He had served since April 2008 as 16th president of what is formally known as the Church of Jesus Christ of Latter-Day Saints.

Monson died on Tuesday at his home in Salt Lake City, Utah, U.S., where the church is based.

Presidents are considered prophets and serve as both religious and administrative head of the Mormon Church, which has about 16 million adherents worldwide.

Joseph Smith, the church’s 19th-century founder, was the first president.

Monson had been a member of the church’s top leadership circle since October 1963.