Halifax Regional Police are warning that a 55-year-old high-risk offender is set to be released in the Halifax Regional Municipality after serving 20 years in prison for a string of rapes in Toronto.

Douglas Gladstone Burden is to be freed Tuesday on series of conditions, and will be staying at a halfway house near Dalhousie University.

The university said it has sent a security bulletin to all students and staff. The bulletin is being “reinforced” with students living in residence and will be posted around campus. The university said it is also taking to social media to alert people.

Police said they are worried that Burden will re-offend. The force said it will be monitoring his progress, and doing spot checks with a special high risk enforcement team.

The conditions of Burden's release include:

Having no contact with victims.

Residing at a specific place approved by the Correctional Service of Canada.

Reporting any relationships with women — sexual or otherwise — to parole supervisor.

Avoiding drinking establishments such as bars, clubs and taverns.

Providing detailed financial information to parole supervisor.

Police said Burden was convicted on a number of charges including administering a noxious substance, seven counts of unlawful confinement and nine counts of sexual assault in 1992.

The offences took place over a three-year period, with convictions relating to 11 victims between the ages of 20 and 39.

According to parole documents, Burden would meet young women in a bar or restaurant promising the chance at a job.

He would then spike their drinks "with a drug that would reduce their ability to remember," making them easy targets . The documents said Burden would take the women back to his apartment where he would sexually assault them.

The victims would wake up with little memory of what had happened.

A police statement referred to him as a "high-risk offender."

Psychological assessments presented to the parole board say Burden suffers from narcissistic personality disorder. They go on to say he has difficulty establishing interpersonal relationships — particularly with women — as well as having a controlling attitude and difficulties with authority.

Halifax police said based on Burden’s criminal history they’re concerned he’ll reoffend, but warned against any vigilante retaliation from the public.