The mother of a murdered Toronto teen said she's gotten some mysterious phone calls since her son was shot to death last year.

Betty Gyamfi said someone called her, claiming to know who killed her son, 19-year-old Richard Gyamfi.

The caller never identified himself but police say they are looking to speak to anyone who can give them information on a man named "Chambers."

On Monday, Toronto police Det. Peter Moreira spoke to reporters outside the Jane Street building where Gyamfi was shot on Sept. 28, 2007.

He said a $50,000 reward is being offered for information leading up to an arrest in the case.

He also told CTV Toronto that the gun used in the murder has been linked to another shooting outside the city.

"We are appealing to members of the Jane-Finch community to come forward with the vital clue we know exist within people who live in this area," he said from the scene of the murder. "The info we're looking for will help us solidify our case and help us make an arrest."

Gyamfi died from a gunshot to the head on Sept. 28, 2007. He was found slumped against the wheel of his car at the back of a highrise located at 2999 Jane Street, near Finch Avenue. Police say they believe Gyamfi was approached by two suspects.

"He said he was going downstairs," recalled Gyamfi's mother about that fateful night. "I said, 'Richard, stay here, I need you.' He said, 'Mom, I'll be back.'

"He never came back," she said.

Moreira said investigators found several clues and had identified a number of persons of interest. However, detectives didn't have enough witnesses to make an arrest.

Three of Gyamfi's friends were in the car when he was shot.

"I asked them, why don't you people want to share?" she said. "They say they are scared, that maybe they will kill them."

However, police now have new leads.

"A forensic link has helped us narrow our focus," Morreira said. "This new information has allowed us to open up avenues to investigate additional witnesses."

Police put up posters around the community announcing the reward.

They said the teen was well-liked in the area and had no criminal record.

Anyone with information is being asked to call the homicide squad at either 416-808-7394 or 416-808-7414. Anonymous tips can be left with Crime Stoppers at 416-222-TIPS.

With a report from CTV Toronto's John Musselman