Thomas Gilbert, who founded $200m (£130m) hedge fund Wainscott Capital Partners, has been killed after being found shot in the head at his flat in Manhattan, New York, yesterday.
New York City Police Department said his son Thomas Gilbert Junior, 30, had been taken in for questioning but not charged with a crime.
Earlier, police spokesman Lieutenant John Grimpel said:
Right now, we're looking to speak to this son, who was the last person to see him alive.
Thomas Gilbert Senior, 70, was shot in the back of the head around 3:30pm EST (8.30pm GMT) inside his bedroom at the flat and a Glock 22 .40-caliber handgun has been recovered from the crime scene.
Gilbert Senior had studied at Princeton University and Harvard Business School before an illustrious Wall Street career.
He founded Wainscott in 2011 after leaving private equity biotech and healthcare fund Therapeutics Syzygy Therapeutics, which he'd co-founded.