COOK COUNTY CRIMINAL COURTHOUSE — Prosecutors have charged an 18-year-old Jefferson Park man with murder after he fatally shot his 17-year-old brother.

The siblings, Brad and Ryan Nicholson, were arguing inside their bedroom about 3 p.m. Friday when their parents heard "a single loud sound," Assistant State's Attorney Jennifer Walsh said during a bond hearing Monday.

Brad Nicholson, 18, began to scream, she said.

According to prosecutors, Brad Nicholson had shot his brother, 17-year-old Ryan Nicholson, once in the head with a loaded .45 caliber handgun that was in the bedroom.

It's not clear why the gun was in the room. Brad Nicholson later told police the gun belonged to him, but he did not have a valid FOID card, court records show.

Ryan Nicholson suffered one through-and-through gunshot wound in his hand and an entrance wound in his head, Walsh said. Authorities recovered a bullet in the boy's brain, she added.

Prosecutors argued that Ryan Nicholson had been holding his hand in front of his face "in a defensive posture" when he was shot. The bullet went through the boy's hand, Walsh argued, and lodged in his head.

But Assistant Public Defender Lisa Bream said Brad and Ryan Nicholson were struggling over the gun when it accidentally went off.

As Bream stood before Cook County Judge Donald Panarese Jr. on Monday, she pointed to Brad Nicholson's face, to bruises around his eye, and said they were consistent with a struggle.

"This is a horrible family tragedy," Bream said, noting that Brad Nicholson had no criminal record, and both of his parents were in court to support him.

Tears streamed down his mother's face Monday as attorneys recounted facts for the judge.

According to an arrest report, Brad Nicholson hid the gun after the fatal shooting. Police later recovered the .45 caliber semiautomatic weapon, and Nicholson admitted ownership, the report said.

Brad Nicholson, of the 5100 block of North Austin Avenue, was arrested Friday and charged with first-degree murder.

On Monday, Judge Panarese ordered the teen held in lieu of $750,000 bail.

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