Sharon Clahar, who was taking piano lessons, is accused of ambushing her piano teacher and repeatedly stabbing her. (Source: Miami-Dade Corrections Dept.)

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NORTH MIAMI BEACH (CBSMiami) — A woman taking piano lessons is accused of ambushing her piano teacher and repeatedly stabbing her.

“It was just so scary,” said a young woman who didn’t want to be identified.

She witnessed a violent attack in the North Miami Beach office building where she works. She told CBS4’s Natalia Zea she can’t get the screams she heard out of her head.

” I just heard someone screaming hysterically,” said the woman.

She said she saw 41-year old Sharon Clahar standing over the victim, her piano teacher, with a large knife stabbing her.

Click here to watch Natalia Zea’s report.

“It was repeated and the lady you could see she was struggling….(the victim) was screaming and telling us to help and she was bleeding and call 911 and I was yelling.”

Employees told Zea that Clahar was waiting inside a dentist’s office next door to the piano lesson studio. She was calm, said she had an appointment, and the employees did not see a knife. They say when the piano teacher came to open up her studio, Clahar attacked.

According to police, the witness convinced Clahar to stop the assault.

“I yelled for her to stop, and from my yell from her to stop, I just ran to try to get someone to call police.”

Investigators said Clahar did stop then. But the witness was also disturbed by her demeanor once the violence was over.

“We see her walking down the hallway with the knife in her hand. She was so calm. Too calm. Too too calm. She said nothing. So I told my coworker ‘that’s her, hurry up and lock the door,’ because I saw her trying to open the dentist’s door. So I didn’t know what she was gonna do next,” said the witness.

Police caught up to Clahar outside the building and charged her with aggravated assault with a deadly weapon. The young woman told Zea that based on what she saw, she believes the charge should be attempted murder.

“When I saw (the victim) it was just blood everywhere so we didn’t know where it was coming from….I’m just glad she’s alive.”

Police are not identifying the piano teacher, but said she was stabbed several times in the upper arm area and is expected to be okay. Employees in the office building said she had just recently started giving piano lessons there.

Clahar is being held on $10,000 bond and is expected to face a judge on Thursday.