Authorities searching for the elusive Unabomber, whose mail bombs have killed three people and injured 19 since 1978, are focusing on a former member of the Symbionese Liberation Army, the terrorist group which kidnapped the heiress Patti Hearst two decades ago.
James William Kilgore, 48, who has been on the run since a bomb attack in 1976, is said to be top of the FBI's wanted list. Those familiar with the case note that the Unabomber started to send his bombs in 1978, not long after Mr Kilgore disappeared, vowing to attack the government.
Officially, Mr Kilgore remains "a potential suspect". Those who knew Mr Kilgore saw him as an idealist among radicals and an unlikely serial killer. "At least if they find him, they could decide whether he is the guy," a law official said.
The investigation into the Unabomber has been stepped up since last month's threat to blow up a plane threw Los Angeles airport into chaos. San Francisco radicals have been investigated, but so far Mr Kilgore is the only firm suspect.