The man who stole the rings right off the fingers of a fragile grandmother recovering from a leg amputation is a professional thief, says the hospital's security manager.

Paladin Security head Leo Knight believes his staff have encountered the thief before, stealing from the vulnerable at hospitals across B.C.'s Lower Mainland.

"We believe he's been involved in a number of cases over the last couple of years," he said.

Over the weekend, a thief pretending to be a ring cleaner pulled three priceless rings off the fingers of 91-year-old Agnes Ulmer as she lay in her Vancouver General Hospital bed.

The man was caught on a security video, but kept his head ducked low.

While a CTV News crew was visiting Ulmer yesterday, security staff showed Ulmer a picture of a suspect that has a history of stealing from vulnerable hospital patients.

In 2006, a man asked to clean a patient's ring at St. Paul's Hospital. That time, the patient didn't hand the jewelry over but reported the incident instead. The suspect was long gone.

Fraser Health confirms the same scam was pulled -- this time successfully -- at Surrey Memorial back in 2005. A patient there handed rings over to be cleaned and never got them back. The man was never caught.

Paladin Security provided the picture to the Vancouver Police, and investigators recognized the man right away, said Const. Tim Fanning.

"We do have a prime suspect," he said. "But there are other people that may be involved, so that's what the detectives are doing right now -- sorting it all out and piecing the file together."

With a report from CTV British Columbia's Rob Brown