An agonized FDNY lieutenant Tuesday described watching two colleagues jump to their deaths from a burning Bronx building in the Black Sunday fire.

Lt. Kevin White told a rapt court that several firefighters desperately tried to escape the fire-engulfed E. 178th St. building by climbing out fourth-floor windows.

He watched in horror as the cornered heroes jumped 50 feet to a concrete courtyard.

"I gave a mayday, 'Man down in the rear,'" White said. "That's when the first (firefighter) dropped. Then another. They continued to fall."

White appeared on the second day of the trial of two building tenants and a manager accused of illegally subdividing apartments into dangerous warrens of rooms.

White admitted being "transfixed" by the sight of fellow firefighters plunging from the Tremont building.

Lt. Curtis Meyran and Firefighter John Bellew died from their injuries; four others were badly hurt.

White, who worked at Ladder 56, was part of a backup fire company called in as the blaze raged out of control on Jan. 24, 2004.

There was only a small amount of smoke visible from the front of the building but billowing smoke was pouring from the back.

"Things started to go bad quickly," he said.

Trapped firefighters pleaded for oxygen and for help opening up the roof. Then they started clambering out the windows, even though they knew they faced long odds of survival.

"I saw (firefighters) in distress in each of the top-floor windows," White said. "One was hanging straight down, held by two others."

White ordered a 35-foot portable ladder and ropes brought from his fire truck in hopes of giving the firefighters some chance of climbing to safety.

"They came with the ladder, but it was too late," he said.

One jury will decide the fate of tenants Caridad Coste, 58, and Rafael Castillo, 57, who face manslaughter and other charges that could put them behind bars for 15 years.

A second jury will render a verdict on the same charges against building manager Cesar Rios, 52, and the company that owns the building.