A 42-year-old District firefighter died yesterday of a brain injury that was apparently received during a fire department swimming class Monday, causing many firefighters to angrily attack the department for forcing him to to take the rigorous course.

Clifford R. Oliver, a 20-year member of the department and a rescue squad driver for Rescue Squad No. 3 in the 2100 block of 14th Street SE, had just completed a swimming exercise at a D.C. Department of Recreation facility on North Carolina Avenue SE when he complained of headaches and dizziness, firefighters said.

During the exercise, Oliver swam 20 laps and retrieved a 10-pound brick, according to firefighters.

He was participating in his first day of an advanced lifesaving course given by the fire department and administered by the Recreation Department. The program was started after the department was criticized in August when a helicopter crashed in the Potomac River, killing three persons and injuring a fourth.

Union officials complained at that time that two members of the D.C. fireboat service could not swim, sharply reducing their effectiveness in any river rescue operation. In September Mayor Marion Barry ordered that all firefighters assigned to fireboats must receive enough swimming lessons to be certified as life guards.

But firefighters questioned why Oliver, who was not assigned to a fireboat, was ordered last week to take the intensive five-day advanced lifesaving course. He was expected to retire in May and repeatedly asked officials to exempt him from the course.

A firefighter who worked with Oliver last weekend said that "he was apprehensive and didn't want to take the course because he knew he wasn't in the best physical shape." As the driver for a rescue squad, Oliver felt that his chances of using advanced swimming skills "were remote," the firefighter said.

Fire department officials wouldn't comment yesterday. A spokesman said Fire Chief Theodore R. Coleman would make a statement today.

Oliver apparently mentioned that he had a headache and was sick to his stomach during a shower on a lunch break, according to firefighters. He collapsed and stopped breathing, but was resuscitated at the scene by other fire department members.

Oliver was taken to the Capitol Hill Hospital emergency room about 11:30 a.m., according to hospital officials. He was suffering from massive hemorrhaging in the brain caused by arterial bleeding, according to Dr. Morris Jutcovich in the hospital's intensive care unit.

Jutcovich said he did not know what caused the bleeding, but it occurred within 30 minutes preceding Oliver's collapse.

After about four hours of surgery, Oliver's condition stabilized, but during the night it deteriorated. It was discovered yesterday that bleeding had developed in a different and deeper part of the brain that could not be repaired by surgery, Jutcovich said. By 2:41 p.m., doctors determined that no blood was flowing to Oliver's brain, and he was pronounced dead of massive cerebral stem hemorrhaging.

"We're all grieving over the loss of one of our own, a member of the family," said Thomas Tippett, president of the International Association of Fire Fighters, Local 36, which represents most firefighters. "We've had discussions with the department and they've promised full cooperation in investigating his untimely death.

"He was a fireman's fireman," said Ken Cox, vice president of the union and a firefighter who worked closely with Oliver. "He was a guy you could always count on, who excelled in all aspects of rescue squad work. We called his squad Ollie's Trolley."

Oliver's wife and two children donated his heart and several other organs for medical purposes, as he had requested.

"That was a tremendous thing to do," said Jutcovich. "We always have shortages of organs and people waiting. Despite all of their grief, they didn't think of themselves -- they thought of others."