A civilian interpreter crashed a stolen truck Wednesday at Camp Bastion and set himself afire as military officials stood nearby waiting to greet Panetta, who was arriving in Afghanistan on an unannounced visit.
The man suffered burns over 70 percent of his body and died Thursday, officials said.
Navy Capt. John Kirby, a Pentagon spokesman, told reporters the man tried to run over several high-ranking Marine officers.
"He took a vehicle by force, drove it onto a ramp, at a high rate of speed, drove it at individuals who had to get out of the way to keep from getting hit by it, and then a flash of smoke and fire in the cab," Kirby was quoted as saying by The Washington Post.
Panetta's plane was diverted to another parking ramp, officials said.
"I have absolutely no reason to believe that any of this was directed at me," Panetta told reporters Thursday before he left Afghanistan. "Whatever happened here was directed at others who were there on the field, not me or my plane or anything associated with me."
News of the attack was withheld for 10 hours from reporters who were traveling on the plane with Panetta, the Post said.
Kirby said investigators were unable to interview the suspect before he died.
"There's reason to believe he intended harm," Kirby said. "We can't interview him, so I don't know that we're going to get much more."
He said military officials don't have any indication the man knew Panetta was on the plane.
Afghan President Hamid Karzai told Panetta Thursday U.S. troops should leave outposts in Afghan villages and return to their main bases.
Karzai said Afghans no longer trust in international forces, the presidential palace said in a statement.
His comments came days after a U.S. soldier was accused of leaving his outpost and killing 16 Afghan men, women and children in their villages.
The soldier who allegedly killed the Afghans in Kandahar province has been moved to Kuwait, the Post reported.