The former top executive of American International Group Inc. plundered an AIG retirement program of billions of dollars because he was angry at being forced out of the company, a lawyer for AIG told jurors Monday at the start of a civil trial.

Attorney Theodore Wells told the jury in Manhattan that former AIG Chief Executive Officer Maurice "Hank" Greenberg improperly took $4.3 billion in stock from the company in 2005, after he was ousted by the company amid investigations of accounting irregularities.

"Hank Greenberg was mad. He was angry," Wells said in U.S. District Court of the emotional state of the man who, over a 35-year-career, built AIG from a small company into the world's largest insurance company.

Wells said that Greenberg, within weeks of being forced out in mid-2005, gave the go-ahead for tens of millions of shares to be sold from a trust fund. The fund was set up to provide incentive bonuses to a select group of AIG management and highly compensated employees that they would receive upon their retirement.

Greenberg, 84, has contended through his lawyers that he had the right to sell the shares because they were owned by Starr International, a privately held company he controlled.

Starr International was named after Cornelius Vander Starr, who created a worldwide network of insurance companies in the early 1900s.

AIG maintains that Starr and Greenberg, his protege and successor, decided in the late 1960s to organize the various companies under one holding company, AIG.

Starr International remained a private company and its shareholders decided in 1970 that the amount that its shares of AIG were worth above book value of about $110 million should be used to compensate AIG employees, AIG has said.

The embattled insurer is trying to reclaim the money from Starr it says was wrongly pocketed through stock sales by Greenberg.