By Joe Holden

CAMDEN, N.J. (CBS) — It was a July morning in Camden when 53-year-old Ed DuPont was outside of a convenience store and without warning, he was attacked. He died weeks later.

His killer is still out there but newly-obtained surveillance video shows the man police want to track down.

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Tuesday, July 6, just after 9 in the morning, 53-year-old Ed DuPont is chatting with people outside this Camden convenience store at 7th and Pine Streets.

Surveillance video provided by the Camden County Prosecutor’s Office Homicide Unit to CBS3 Mysteries and seen for the first time shows DuPont on his bike. He’s talking to a woman when a man approaches from behind and attacks him.

“A suspect comes up, punching him one time,” Det. Lance Merrill said. “Mr. DuPont falls, hits hit head on the concrete and never regains consciousness.”

“Cowardly move, to attack somebody from behind,” Ed’s sister, Angela, said.

He was left in a coma for three weeks before he eventually died.

“Once his head hit the concrete, he was unconscious and unfortunately he passed away,” she said. “It’s just a sad series of events and every day I talk to him and I tell him, ‘we’re doing everything, we’re doing everything,’ because he didn’t deserve this.”

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Investigations say the crime was entirely unprovoked.

After speaking with eyewitnesses, detectives still can’t explain why this happened.

They have a good idea of who the attacker is but need more information to make an arrest.

“No one deserves this,” Angela said.

DuPont is described as a man who loved life, his talents in the use of his hands in hairstyling and cooking.

“He was happy. He had a gift of gab like he could charm you out of anything and people liked him,” Angela said. “And I know where this incident took place, that someone had to see something. It’s a heavily trafficked area, foot traffic all the time. Someone knows, someone saw.”

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Investigators are offering a $1,000 reward for information. If you know anything about the man seen attacking DuPont, call Merrill at 609-789-3766.