It began when the Maryland Department of Corrections bus carrying six prisoners tried to pass Gerald Krizan's sports car on the outskirts of Baltimore on Tuesday.

It ended 15 minutes later, after a wild 70-mile-an-hour chase through suburban traffic, when Krizan said he stopped for a stoplight and three prison guards leaped from the pursuing bus and beat him at gun point.

Corrections Department officials confirmed yesterday that all three guards on a department bus were involved in a "fight" with Krizan following an alternation on the highway.

"We do not condone this type of behavior," said Elmanus Herndon, acting deputy commissioner of the department. He said that a full investigation is being conducted and disciplinary action is likely since the guards admitted leaving the prisoners unguarded "momentarily" during the fight.

The "fight," according to accounts by Krizan, a University of Maryland law student and several other witnesses interviewed yesterday, consisted of two of the three correctional officers beating Krizan while the third pointed a shotgun at him.

Krizan, who lives in Laurel, said the incident began on the Baltimore-Washington Parkway when the bus tried to pass him and nearly struck his car. When the bus finally was able to pass, the bus door was open and the bus driver was yelling obscenities at him, he said. Krizan said he dodged an object thrown at him and threw a soft drink back.

The full-sized bus with its load of prisoners then chased Krizan through suburban Baltimore traffic until he stopped at a traffic right where the witnesses said Krizan was beaten.

"It was just plain bad judgment," said Herndon yesterday.