A 21-year-old man was shot and killed "execution style" in Philadelphia on Sunday while talking to a candidate for the Pennsylvania House.

Police said the the unidentified 21-year-old man was shot while speaking to Democratic candidate Chris Rabb about the state's upcoming primary.

Police said the gunman shot the victim twice in the head. He was pronounced dead at the scene.

A spokesman for Rabb's campaign, Chris Visco, said the the victim told Rabb that he was planning to work the polls on Tuesday.

"He was talking to a voter, a nice young man who works the polls on election day. They were talking about the election. The young man was interested in Chris' campaign and his candidacy for the 200th," Vicso told WPVI-TV.

"One of the people that was with (Chris) handed him a piece of literature, took his phone number, and another young man came up behind him and shot him execution style in the head," he told the televison station.

Rabb is running for a seat in the 200th District, and was canvassing the area at the time.

Visco told Philly.com that Rabb and another campaign worker - both of whom witnessed the shooting but were not injured - were still speaking with detectives Sunday evening and were in shock.

"The [victim] had been shot, execution-style, blood gushing everywhere," Visco told Philly.com. He added that he spoke with Rabb Sunday night, who was 'devastated."

Police told Fox 29 the shooter appears to be a black man, described as 6'0' wearing a light grey hoodie.

A motive for the shooting remains unclear. No arrests have been made.

The Associated Press contributed to this report.

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