Police said Michael Nash, 27, of Arlington, was walking with a woman when he began to physically and sexually assault her. Patricio Salazar, of Arlington, saw the assault and tried to help her.

WASHINGTON — An Arlington, Virginia, man is dead after he tried to stop a sexual assault he witnessed Thursday night. The suspect, who assaulted multiple people and robbed another, is in custody, police say.

Arlington County police were called to the 1300 block of S. George Mason Drive shortly before 9:30 p.m.

Police said Michael Nash, 27, of Arlington, was walking with a woman when he began to physically and sexually assault her.

Patricio Salazar, 54, of Arlington, saw the assault and tried to help the victim. Nash then physically assaulted Salazar and left him unconscious, the police said. Salazar was taken to a hospital, where he died.

Nash ran off, and approached two other people, whom he tried to rob of a cellphone. The victims fought back. Nash fled on foot and then robbed another woman of her phone.

Nash was arrested and charged with abduction and multiple sex crimes, with additional charges still pending, police said. He’s being held without bond.

“It’s absolutely tragic,” said Ashley Savage, an Arlington County police spokeswoman. “If you see something, call police immediately.”

Below is a map of where the assault happened.

WTOP’s Megan Cloherty contributed to this report.