(STMW) — On Aug. 27, 2014, Hector Rivera waited outside the workplace of a woman he had been dating in Albany Park, and when he saw Erendira Pimentel-Hernandez, he stabbed her more than 20 times.

On Friday, the 56-year-old Rivera was sentenced to 30 years in prison after pleading guilty to murder for the fatal stabbing, according to a statement from the Cook County state’s attorney’s office.

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Pimentel-Hernandez, 38, had been dating Rivera when he met her about 8:15 a.m. that summer morning in a stairwell in the 4700 block of North Lawndale, prosecutors said. She was a caretaker for a senior who lived on the block.

A witness said she saw the victim talking to a man in a rear parking lot, according to a police report. The two then walked into the stairwell and closed the door.

Rivera had “stabbed her repeatedly before fleeing,” prosecutors said. “The victim suffered numerous wounds to her face, torso and arms…”

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The witness heard Pimentel-Hernandez scream and saw the man leave the stairwell and walk to a parked pickup. He told the witness, “You tell police, I’ll get you next,” according to the report.

Several other witnesses were also present and positively identified Rivera, prosecutors said. When he was arrested three days later, he admitted to police that he had “stabbed and killed” Pimental.

Pimental-Hernandez, of the 5000 block of West Grand, was taken to Advocate Illinois Masonic Medical Center, where she died at 12:40 p.m. that afternoon, according to the Cook County medical examiner’s office. An autopsy confirmed she died of multiple stab wounds.

Cook County Judge Thomas Gainer sentenced Rivera to 30 years.

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(Source: Sun-Times Media Wire © Chicago Sun-Times 2015. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)