The city police department marked the 30-year anniversary of a rookie officer's death with a street sign dedication ceremony in Queens on Monday.

22-year-old Officer Edward Byrne was fatally shot in the head on this day 30 years ago as he sat in his patrol car, protecting a witness who had complained about drug activity in the neighborhood.

A section of 91st Ave. near 168th St. in Jamaica was renamed in honor of the officer in a ceremony that Mayor Bill de Blasio, Police Commissioner James O'Neill, and other police officers attended.

Byrne's murder prompted national outrage. Five men remain behind bars for the killing.

Byrne's brother, Lawrence, who is now the NYPD Deputy Commissioner for Legal Matters, described Byrne's encounters with the people who eventually took his life.

"He had tried to chase the drug dealers away. He had fought with them. He called the police," said Byrne's brother, Lawrence, who is now the NYPD Deputy Commissioner for Legal Matters, describing Edward Byrne's encounters with the people who eventually took his life.

"He agreed to testify against them, and in response the drug dealers threatened him and they firebombed his house twice," Lawrence Byrne continued.

Hundreds of police officers also gathered overnight for a candlelight vigil at the spot where Officer Byrne was killed.