NEW YORK (AP) _ The driver of a runaway bus that killed a messenger and critically injured a bicyclist on Fifth Avenue probably had seizure, not a heart attack, The New York Times reported today.

Driver Charles Alston's neurologist, Dr. Orrin Devinsky, told the Times Alston experienced ``events consistent with seizures'' during last Thursday's crash, and had suffered several similar episodes in the past.

``These are events consistent with seizures, but by no means are they known to be seizures,'' he said.

Devinsky said he hopes to know in three or four days what caused the episode. Possible explanations include epilepsy and heart arrhythmia, he said.

``We're trying to catch an event or other electrical abnormalities that might tell us what happened,'' Devinsky said. ``At this point we don't have any answers.''

Alston's stepdaughter said on the day of the crash that he had suffered seizures that he thought were caused by epilepsy, but she and other relatives later deemphasized his medical condition.

Alston, 55, also has had throat cancer for several years.

The transit authority has said he never told its doctors that he had suffered seizures.

Alston's bus killed a delivery man, Alexis Castro, 39, of Queens, and critically injured Neil MacFarquhar, 38, a Times reporter who was riding a bicycle down the avenue.

MacFarquhar remained in critical condition Monday, the Times said.

Willie James, president of the Transport Workers Union, said Alston remembered very little about the accident.

``All he remembers is that he blacked out and the next thing he knew they were taking him out of the bus and he was in a hospital,'' he said.