IN OVERBROOK yesterday, those who loved and mourned Dennis Gore Jr. were filled with questions:

Why had a gunman approached Gore on a street near his home Monday afternoon and fired five shots into his body without saying a word?

Who would want to hurt the gentle man with a steady job and two small children?

How would his family go on without their beloved son and brother?

Gore, son of a veteran Philadelphia police officer, was 24. Police yesterday were asking for the public's help in tracking down his killer.

"It's a mystery to us," said Homicide Capt. James Clark. "Right now, we have no idea why someone would do this."

Gore and his girlfriend had just bought lunch at a corner store and were walking back to his house when they were approached by an armed stranger on 55th Street near Hunter, police said.

The man fired five bullets into Gore's body at point-blank range. The gunman fled as Gore fell to the ground.

"He didn't say a word," Clark said of the gunman. "This was a tragic and senseless murder."

In front of Gore's home yesterday, rows of candles lined the sidewalk, and three large photos of Gore were displayed on the small front lawn. Gore's brother said their mother wasn't up to speaking with a reporter.

Gore, he said, worked at a nursing home.

The Fraternal Order of Police is offering a $5,000 reward for anyone with information leading to an arrest in the case. An additional $20,000 reward is being offered by the city to anyone who provides information leading to arrest and conviction.

Police described the gunman as a thin black man, 5 feet 7, with a goatee. He wore a gray hooded sweatshirt, blue jeans, black Nike sneakers and a black hat, and was armed with a silver revolver.

Tipsters should contact the Homicide Division at 215-686-3334.