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Stephanie Wydra testified Friday that she found in her ex-boyfriend’s bedroom a plastic bag filled with $15,000 in cash after he told her to destroy one of his bloody T-shirts.

The boyfriend, Christopher Wyma, later told her about the troubling thoughts he had been having, Wydra said.

Wyma and John Granat Jr. are on trial for the Sept. 11, 2011, slayings of Granat’s parents, Maria Granat and John Granat Sr., in an unincorporated area near Palos Park.

“He just blurted out, ‘I can’t get their screams out of my head,’ ” Wydra told Cook County jurors.

Two of 21 stab wounds inflicted on Maria Granat while she was lying in bed punctured her lung, according to testimony Friday in Cook County court.

The wounds likely would have led to her making sounds commonly referred to as a “death rattle,” said Dr. James Filkins, the former deputy medical examiner who performed autopsies on the victims.

Earlier this week, Cook County jurors watched a video recording of an October 2011 interview of Wyma, then 17 years old, in which he described to police the “tiny little noises” Maria Granat made while dying.

Prosecutors allege a 17-year-old John Granat Jr., angry after his parents grounded him, groomed his friends to help beat and stab his parents to death. Maria Granat had caught her son growing marijuana plants in his bedroom and punished him, prosecutors said.

Wyma and Granat Jr., both now 22, and two other friends also took tens of thousands of dollars in cash kept in the home, prosecutors said.

Wyma’s defense has argued that he did not kill the Granats but was there that morning and displayed “poor judgment” by helping destroy evidence. An attorney for John Granat Jr. has argued that evidence shows Wyma and another friend, Ehab Qasem, killed the Granats, and suggested that John Granat Jr. treated his friends well because of his family’s wealth.

Prosecutors allege Wyam and Qasem, 24, of Hickory Hills, who is expected to testify next week, crept into the bedroom and attacked the couple with metal baseball bats while John Granat Jr. remained in the family garage counting money.

Qasem’s testimony is part of a deal with prosecutors to plead guilty to murder in exchange for a sentence of 40 years in state prison.

Mohammed Salahat, 22, of Palos Heights, was sentenced to 35 years in prison last year after pleading guilty to his role as the group’s getaway driver.

Prosecutors allege all four of the men met the night before the killings at Wyma’s house, which was known to their group of friends as the place to smoke marijuana.

On Friday, Wydra, who had dated Wyma for about three months, said she watched from a short distance the meeting that, prosecutors said, sparked the series of events that weekend leading to the slayings.

Wydra told jurors she overheard the boys say, “It is happening tonight. This is on.”

The trial is scheduled to continue Tuesday.

Nick Swedberg is a freelance reporter for the Daily Southtown.