A child’s chilling screams to two 911 dispatchers that he had been raped by an intruder and his dad was “dying on the floor,” were played today for a Woburn jury on the first day of testimony in an attempted-murder trial.

“Dad, are you OK?” the then 11-year-old son of a Harvard researcher could be heard whimpering during his taped Aug. 26, 2010, call to state police dispatcher Patricia Furdon from a Cambridge bedroom, where his nearly-decapitated father was bleeding out at his feet.

“The officers who showed up could not tell the ethnicity of the father. He was totally covered in blood. The young son was standing there, crying, totally covered in blood. This is what this is about,” assistant Middlesex District Attorney Thomas P. O’Reilly told the jury.

Former construction worker Marcos Colono, 35, who is representing himself at Middlesex Superior Court, is accused of breaking into the former Pearl Street apartment of the boy’s now 55-year-old father masked and clutching an 8-inch butcher knife before attacking them both, all while eerily addressing them as “father” and “son,” O’Reilly said.

Colono is the brother of Michael Colono, who on April 12, 2003, was fatally stabbed by well-to-do Harvard graduate student Alexander Pring-Wilson during a confrontation on the streets of Cambridge. Pring-Wilson pleaded guilty to involuntary manslaughter in 2008.

Judge Thomas P. Billings ordered that neither alleged victim be photographed by news media or mentioned by name.

O’Reilly said the child lived with his mother, but on Aug. 25, 2010, asked to have a sleepover at his dad’s place.

The prosecutor said Colono, in search of money, broke in between 11:30 p.m. and 1:15 a.m. Aug. 26.

“Where’s the money?” O’Reilly said Colono demanded. “He made the father crawl to the kitchen, then made him crawl back.”

Then, with the father in the same bedroom, O’Reilly described in horrid detail how Colono twice raped the boy with a knife at this throat.

The child “was held by the threat of death if he didn’t do what he was told,” O’Reilly said. “Then the 11-year-old watched his father brutally stabbed, losing half his blood supply.”

The father, in a near-death struggle with Colono, had his neck hacked and slashed as many as 11 times, O’Reilly said.

When the child was transferred to a Cambridge police dispatcher by Furdon after his 911 cell phone call automatically went to state police, he said through tears, “My dad is dying on the floor. Please come fast!” He then hung up.

Colono, in a tailored gray suit and blue shirt, did not give an opening statement to the jury, telling Billings he was reserving his right to do so until he put on his defense.

Colono is charged with two counts of aggravated rape of a child with force, home invasion, armed assault with intent to murder, aggravated assault with a dangerous weapon and assault and battery with a dangerous weapon.

In addition, separate charges of aggravated rape, home invasion, armed burglary and assault with a dangerous weapon await Colono in Suffolk County pertaining to the alleged rapes of two female college students in Brighton in 2008.