The shooting death of a motorist by police during an overnight traffic stop in December was a tragedy, not a crime, Philadelphia’s district attorney said Thursday.

Surveillance footage corroborated the officers’’ story that Brandon Tate-Brown, 26, was reaching back into his car for a loaded pistol when an officer shot and killed him, District Attorney Seth Williams said.

"The facts show a tragedy, a terrible tragedy, but not a crime," Williams said at a news conference.

An officer shot Tate-Brown once in the head after pulling him over at 2:45 a.m. Dec. 15 for driving without his headlights on, police say. Tate-Brown also had several prior arrests.

"He broke away from officers three separate times," Williams said. "He went around the car towards the passenger side where he tried to reach inside to the place where he knew he had put his gun."

Williams said he spoke with Tate-Brown’s family before announcing the findings.

Tate-Brown’s mother, Tanya Dickerson, along with the family’s attorney, Brian Mildenberg, told reporters Thursday they plan to file a civil rights lawsuit.

"Like any mother, I choked and I cried," Dickerson said when she found out that charges would not be filed.

Mildenberg said the family wants to know why Tate-Brown was pulled over and whether the use of deadly force was justified.

Thursday night, protesters interrupted a community meeting at Lawncrest Recreation Center, attended by Williams and Police Commissioner Charles Ramsey, WCAU television station reported. Fifteen people were arrested after chairs and punches were thrown, but no one was seriously injured, the television station reported.

A woman marching in Philadelphia on Martin Luther King Jr. Day carried a sign bearing Tate-Brown's name as others chanted "Black lives matter!" to protest police killings of black men, including Michael Brown in Ferguson, Missouri, and Eric Garner in New York.  

The officer and his partner were not wounded in the incident in the city's Mayfair section. Police said the officer was placed on administrative duty pending the outcome of the investigation.  

There were 29 officer-involved shooting in Philadelphia last year. Four of them involved a suspect being killed.

The Associated Press contributed to this report