Edward Thomas Mann, charged with killing three persons and injuring 23 others during a siege at the Bethesda offices of IBM, was rushed to Shady Grove Adventist Hospital yesterday morning after going into a fit of rage and possibly attempting suicide, Montgomery County Detention Center officials said.

Mann, 38, who recently told a Montgomery County Circuit Court judge he would like to be executed, caused a commotion in the cell block about 15 minutes after officials told him his mental competency hearings, which had been scheduled for later this month, had been changed to yesterday afternoon.

Mann, who has objected to the competency hearings and has signed a guilty plea, threw a radio at a television set in the cell where he is being held with about 20 other inmates, officials said. Then he slammed his right fist against the television. When guards entered the cell block area, some other inmates told the guards they thought they had seen Mann drink a liquid cleaning solvent a few minutes earlier, according to Samuel Saxton, director of the detention center at Seven Locks Road in Rockville.

After struggling briefly with officials, Mann was rushed by ambulance to Shady Grove, where hospital officials said his stomach was pumped and he was treated for a fractured right hand. Mann was listed in stable condition in the intensive care unit, but a hospital spokeswoman said doctors treating Mann could not confirm whether he had drunk any poison. Any such liquid could have passed through his body by the time he reached the hospital, according to Carol Lee Robinson of the hospital.

"I think it's safe to say the whole thing was triggered by the court hearing," Saxton said yesterday.

Eight doctors were scheduled to consider Mann's mental competency at the hearing. Judge William C. Miller ordered the hearing after eight psychiatrists and psychologists who examined Mann last month could not agree on whether Mann is competent to stand trial.

Mann signed a guilty plea Nov. 25, but Miller said he would not make a ruling on Mann's plea and whether he should be allowed to represent himself until he determines whether Mann is mentally competent to stand trial. Miller ordered the hearings after eight psychiatrists and psychologists who examined Mann last month split on whether they felt Mann was fit to stand trial.

Another hearing has been scheduled for tomorrow. The hearing will proceed, if Mann is released from the hospital, according to the public defender assigned to represent Mann after he fired his first lawyer.

Detention center officials said yesterday was the second time Mann has objected to being brought to a court hearing. The first time, Saxton said Mann said he would not go but he was told he had no choice.