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A North Highlands teen has been arrested on suspicion of murder in the fatal beating of an 86-year-old woman on a high school track near Sacramento, authorities said Friday.

The suspect, 18-year-old Neven Glen Butler, had already been in custody on an unrelated assault and elder abuse charges when he was arrested in the case, according to a news release from the Sacramento County Sheriff's Department.

The two women were attacked as they walked around Highlands High School track shortly after 6 a.m. Wednesday, the Sheriff's Department said. The high school is located in an unincorporated part of Sacramento County.

The victim, 86-year-old Fusako Petrus, was discovered unresponsive by the time deputies arrived following an assault call. Deputies immediately began performing life-saving measures on the victim, but she was pronounced dead at the scene after personnel from the Sacramento Metro Fire Department arrived.

The second victim, a 61-year-old woman, was treated at the scene for her injuries.

According to the Sheriff's Department, the younger woman was initially attacked by the 18-year-old. When Petrus heard the commotion, she intervened and tried to help her friend.

At that point, Butler allegedly sexually assaulted both women before causing the injuries that authorities say resulted in the victim's death.

He then fled the scene.

Butler was arrested later that afternoon after an unprovoked assault left a 92-year-old woman injured in the 2200 block of Northrop Avenue in Sacramento, the Sheriff's Department said.

He was initially booked at the Sacramento County Main Jail on suspicion of felony assault and elder abuse charges.

After he was connected to the earlier incident, he was add-booked on suspicion of murder, the release stated. Butler is ineligible for bail.

His arraignment is scheduled for Monday.

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