Sir Cliff Richard said it is horrifying to think the murderer of his close friend Jill Dando could still be alive and killing other people.
The 37-year-old, then one of the BBC’s highest-profile stars, was shot outside her home in Fulham, west London, on April 26 1999.
Barry George, of Fulham, was initially convicted in July 2001 but was acquitted of killing the presenter at a retrial in August 2008.
On the eve of the 20th anniversary of her murder, Sir Cliff spoke of his shock at his friend’s death, saying: “She was beautiful and she was very bright.
“And somebody killed her… for what reason, what kind of motive could there have been?”
He told an ITV documentary: “It’s for me horrifying to think that that person still is alive and, who knows, maybe killing other people.”
The programme also features an interview with Mr George, who said he found it “overwhelming” and “ludicrous” to be questioned about the murder.
He said: “My conscience was clear – I knew I hadn’t done it.”
Speaking to the Mirror, Ms Dando’s neighbour Helen Doble, who found the presenter slumped in the doorway, said: “That image of her body is burned into my brain.”
She said she was speaking out near the anniversary “because I hope maybe someone will come forward with information that tells us who and why, and then perhaps justice can be done”.
A spokesman for the Metropolitan Police said: “The investigation into the murder of Ms Dando remains an open investigation, and therefore we cannot comment in any detail other than to say we will always explore any new information which may become available.”
Jill Dando – The 20 Year Mystery is on ITV on Thursday at 9pm.