OAKLAND -- The slaughter of two teenage girls near Brookdale Park last November was sparked by an adolescent relationship squabble, a witness testified in court Tuesday.

Raquel Gerstel, 15, and Bobbie Sartain, 16, were gunned down in the early morning hours of Nov. 25 after a teenager they were hanging out with announced that he had another woman coming to meet them, a 16-year-old witness testified in court Tuesday.

The juvenile witness testified that Diantay Powell, 18, told Gerstel and Sartain that he had just invited his girlfriend to hang out with them. That angered Sartain, who slapped Powell and started a fight that led to the killings, the witness said.

The testimony provided the first public explanation for a double murder that left a neighborhood near Brookdale Park shaken. Many residents witnessed the two girls dying on the street from multiple gunshot wounds.

Though Powell and his friend Antonio Edwards, 20, were arrested and charged about two weeks after the killings, questions remained about why the girls were killed.

Police said at the time that the killings were the result of an argument and that Powell was the shooter while Edwards was the getaway driver. Powell was charged with a special circumstances double murder and Edwards was charged with being an accomplice to murder.

Yet, questions remained as to what happened in a white rental car where the teenagers had gathered about 4 a.m., shortly before the killings.

A 16-year-old who was in the car and witnessed the killings reluctantly answered some of those questions Tuesday during a preliminary hearing in the case.

The witness, who is in juvenile detention and is not being named because of his age, initially refused to answer any questions until he was threatened with being held in contempt of court.

On several occasions while testifying, the witness would look at Powell when asked a question and then refuse to answer after Powell shook his head from left to right. Eventually, after several stern warnings from Judge Jon Rolefson, the juvenile began answering questions with his hands over his face.

The witness refused to give descriptive answers but confirmed what he told police two weeks after the killings, including a chilling explanation of how Powell allegedly coldly shot Gerstel in the head after she tried to defend her friend and then ruthlessly gunned down Sartain as she begged for her life.

The witness told police that Sartain slapped Powell after he announced that his girlfriend was coming to meet the group. Powell responded by slapping Sartain, the witness said. At that point, Gerstel came to her friend's defense and was shot in the head, the witness said.

Sartain then tried to run from the scene, the witness said. As she ran, the witness said, Sartain pleaded with Powell not to kill her and said she would not tell anyone what happened.

Powell, however, kept firing, the witness told police. After Sartain fell to the street, Powell allegedly walked over to her and fired three to five more bullets into her body, the witness told police.

A day after the killings, another witness said, Powell acted "hard" and had a demeanor of being satisfied that he had accomplished something.

That other witness, Albert Rich, said Powell told him about the killings the next day while Rich was giving Powell a ride.

"That's the vibe I got, like he thought he accomplished something," Rich said.

Deputy district attorney Ben Beltramo is expected to conclude the preliminary hearing Wednesday. Rolefson then will decide if there is enough evidence to send Powell and Edwards before a jury.