Bill Ackman jabs at old rival Carl Icahn after short-seller Hindenburg's bombshell report

• Bill Ackman said Tuesday that there's a "karmic quality" to Hindenburg Research's attack on his old rival Carl Icahn.
• The two activist investors feuded over a decade ago when Ackman made a $1 billion bet against Herbalife.
• Hindenburg disclosed a short position against Icahn's business empire in a bombshell report published Tuesday.

Bill Ackman took aim at his old rival Carl Icahn Tuesday after short seller Hindenburg Research attacked the latter's business empire.