A Virginia man was beaten to death last week after he tried to intervene to stop a sexual assault, police say.

Patricio Salazar, 54, died at George Washington University Hospital in Washington Thursday night after he was assaulted, allegedly by 27-year-old Michael Nash, Arlington County Police said.

Investigators said Nash was walking with a woman he knew when he started to physically and sexually assault her. Salazar witnessed the assault and tried to help the victim, only to be beaten by Nash, according to police.

A second witness, 27-year-old Brad Flood, told WUSA-TV he went to the scene after he heard the woman screaming.

"I saw a girl, unclothed, sitting there curled up in a ball. And she was the one screaming," said Flood, who added that Nash confronted and threatened him.

"He was like, 'Don’t call the cops. You call the cops, I will end your world,'" Flood said. "He came enough into the light that I could see a bunch of blood on his fists."

Soon after, Flood said he saw Salazar laying on the ground.

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"There was a lot of blood. A lot of blood on his face, his head," Flood said. "I asked if he was OK, he said he was in a lot of pain. He said his back and his head hurt."

Arlington police said Salazar was unconscious when he arrived at the hospital.

"I was able to reiterate to him multiple times that he's a hero," Flood told WUSA. "So at least he heard that multiple times."

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Investigators said Nash took off from the scene of the assault and tried to steal a cell phone from two people. After they resisted, he ran away and stole a cell phone from a woman, police added.

Nash was arrested without incident later that evening and charged with abduction with the intent to defile, forcible sodomy and animate object sexual penetration. Additional charges are pending.

A GoFundMe page created by Flood to raise money for Salazar's family had raised nearly $5,700 of its $10,000 goal as of Monday night. Flood wrote that if Salazar's family declines the money, he will donate it to the victim or a charity that supports sexual assault victims.

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