The man who allegedly fatally sucker-punched a stranger in Queens, N.Y., was arraigned on just an assault charge Tuesday after a count of criminally negligent homicide was dropped by prosecutors, officials said.

Matthew Smith, 42, who turned himself in at the 75th Precinct stationhouse in East New York on Monday, originally was slapped with both counts — but on Tuesday he faced only a charge of assault with intent to cause physical injury.

The DA’s office could not immediately comment on the reason the homicide charge was dropped before his court appearance.

Patrick Gorman was walking near Queens Boulevard and Main Street in Briarwood when he bumped into Smith’s 39-year-old girlfriend, Elena Makarova, just after midnight on June 26, police sources said.

“Excuse me,” said Gorman, 64, before Smith belted him in the face, sources said.

Surveillance video shows Smith punching Gorman, who is seen falling squarely on his back as the duo calmly amble off.

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