PITTSBURGH (KDKA/AP) — A judge has tossed out the case against one of two men accused of killing five people and an unborn baby at a backyard barbecue in Wilkinsburg almost four years ago.

Cheron Shelton, 33, and Robert Thomas, 31, are charged in the March 2016 killings.

(Sketch by Emily Goff)

(Sketch by Emily Goff)

The judge said Monday morning that after reviewing the papers and transcripts over the weekend, he decided to remove Thomas from the case due to a key witness who is no longer testifying.

Following the ruling, both the defense and prosecution asked the judge to dismiss the jury. However, the judge denied that motion.

WATCH: KDKA’s Amy Wadas Reports Live From The Courthouse

Detective Mike Adams was on routine patrol the night of the shooting.

He says he thought he heard gunshots go off so he stopped his car to listen.

During that time, he saw a man getting into a car, stared at him for several seconds, but they never made eye contact.

He says he took off when he heard a woman screaming, but made a mental note of the license plate.

The man in the car is believed to be Shelton, but Adams says it didn’t occur to him that that man was necessarily a suspect in the case at the time.

Thomas’ attorney sought dismissal of the charges against his client after prosecutors decided against putting key Witness Number Three on the stand. That witness allegedly confessed to the killing of a 15-month-old boy during a drive-by shooting at a separate picnic in the East Hills in 2013.

Prosecutors have said they plan to seek capital punishment if the defendants are convicted of first-degree murder.

(Source: Allegheny County)

The proceedings began at 9 a.m., and the commonwealth said Shelton fired 30 bullets.

They said it was a “brazen, vengeful, callous act.”

Defense attorney Randall McKinney said Shelton “played no role in what happened that night.”

One witness, Tonjia Cunningham, went to the barbecue with her friend Tina Shelton.

Tina Shelton was one of the victims who died.

WATCH: KDKA’s Pam Surano Reports Live From Outside The Allegheny County Jail.

Cunningham says she saw someone point a gun over the fence but couldn’t recognize who it was.

She managed to call 911 and the call was played in court.

Shelton and Thomas are charged in the killing of five adults and an unborn child at the cookout on Franklin Avenue in 2016. The shooting injured three others, including a man who is paralyzed.

chanetta powell, brittany powell, shada mahone, jerry shelton, tina shelton

(Images Provided)

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Thomas is expected to walk out of the doors at the Allegheny County Jail on Tuesday.

Day two of the trial begins Tuesday at 9 a.m.

Stay with KDKA for the latest from inside the courtroom during the trial. We will be providing updates on-air and through social media.

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