The vice-chancellor of Queen's University in Belfast (QUB), Professor Patrick Johnston, has died.
Mr Johnston, 58, was appointed vice-chancellor in March 2014.
Previously he was dean of the school of medicine, dentistry and biomedical sciences at QUB and was regarded as one of the world's leading cancer researchers.
The university's registrar, James O'Kane, said the death had caused "a deep sense of shock and loss."
Other members of university staff have also expressed their shock at his passing.
Ulster University vice chancellor Professor Paddy Nixon said: "I am shocked and extremely saddened to learn that Queen's University vice-chancellor, Professor Patrick Johnston, has passed away suddenly.
"My thoughts and sympathies are with his wife and children at this time."
Mr Johnston was also the former director of the Centre for Cancer Research and Cell Biology at QUB.
Since taking over as vice-chancellor in 2014, he had led the university through a period of change known as Vision 2020.
His priorities, as part of that programme, had been to increase the number of international and postgraduate students at QUB and the research income attracted by the university.
The 12th vice-chancellor in the university's history, Professor Johnston was married with four sons.