Widmer died at the age of 52 on Wednesday.
A source told Reuters he had been informed by close friends of Widmer’s family that the banker had committed suicide.
Swiss news Web site 20Minuten cited two unnamed independent sources as saying it was a case of suicide.
Swiss police declined to comment on the death.
Julius Baer, Switzerland’s biggest dedicated wealth manager which has roots dating back to the 19th century, is based in Zurich and manages more than 360 billion Swiss francs ($300.8 billion) in assets for rich individuals and institutions.
A spokesman said there was no link between Widmer’s death and the group’s current activities, but declined to give further details on the cause of Widmer’s death overnight on Wednesday, saying it was a private matter.
The Swiss news agency SDA said Widmer’s wife died from cancer in 2005.
A Zurich-based trader said employees at the bank had been told Widmer had died from an unspecified illness. Widmer, a Swiss citizen, had three children.
“Alex Widmer was the very epitome of a Swiss private banker,” Julius Baer said in a statement.
“It is a great shame,” added a Zurich-based trader. “It is very sad. He embodied Julius Baer. He was the most important person in private banking.”
By 1411GMT, shares in Julius Baer were 9.4 per cent at 33.54 Swiss francs, while DJ Stoxx European banking sector index was down 2.9 per cent.
Widmer will be succeeded by Hans de Gier, who served as the CEO of Julius Baer Group until September 2008 when he stepped down to focus on his role as chairman of hedge fund unit GAM.
“This is a setback for the bank. Widmer is widely regarded as the architect of its new direction,” Claude Zehnder, a ZKB trading analyst said.
“However, with De Gier they have someone very experienced in place who knows the bank inside out,” he said.
Hedge Funds Weighs
Shares in Julius Baer have lost some 60 per cent in 2008 as markets have worried about outflows at its hedge fund GAM, which accelerated in October.
Julius Baer has rejected speculation that it would shed GAM as it restructured its business to focus on wealth management, which has benefited from problems at rival Swiss bank UBS, which has seen strong outflows of money to clients scared by its heavy writedowns.
A GAM spokesman said De Gier will remain as GAM chairman in addition to taking on the Bank Julius Baer CEO role.
One trader said Widmer’s death could lead to “massive uncertainty among investors as a vacuum on the executive level happens in the worst possible time”, adding that takeover rumours could resurface in the future.
But Vontobel analyst Panagiotis Spiliopoulos said appointing De Gier as chief executive was the best short-term solution.
“Julius Baer won’t want to be put under pressure to name a successor. The successor is likely to be a Swiss banker,” he said.
“Widmer made Julius Baer one of the premier addresses for private banking both in
Commenting on Widmer’s death, Chairman Raymond Baer said in a statement: “We have lost a dear friend, a good colleague and a charismatic leader.”
“Alex very successfully opened up new dimensions for the Private Banking business of Julius Baer. His enormous commitment, his active relationship and close involvement with the clients and his passion for banking will forever serve as a model for us,” Baer said.
Widmer joined the Julius Baer Group in 2005 as a member of the executive board and head of private banking and became the chief executive of Bank Julius Baer in November 2007.
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