The general said he didn't know precisely what kind of cancer afflicted Chavez, but added: "He suffered a lot."
He said that Chavez knew when he spoke to Venezuelans on Dec. 8, three days before his final surgery in Cuba, that "there was very little hope he would make it out of that operation."
It was Chavez's fourth cancer surgery and previous interventions had been followed by chemotherapy and radiation.
Ornella echoed the concern of Vice President Nicolas Maduro that some sort of foul play was involved in Chavez's cancer.
"I think it will be 50 years before they declassify a document (that) I think (will show) the hand of the enemy is involved," he said.
The general didn't identify who he was talking about, but Maduro suggested possible U.S. involvement on Tuesday. The U.S. State Department called the allegation absurd.
Maduro, Chavez's self-anointed successor, said Chavez died Tuesday afternoon in a Caracas military hospital.
The government said Chavez, 58, had been there since returning from Cuba on Feb. 18.