A 21-year-old man charged with the second-degree murder of a cancer researcher in downtown Toronto has also been charged in connection with a separate stabbing that occurred the same night, police say.

Mark Ernsting, 39, was fatally wounded outside a home on McGill Street, in the area of Yonge and Gerrard streets, at approximately 9:30 p.m. on Dec. 15.

Emergency crews were called to the scene, where they found the man in life-threatening condition. He was rushed to hospital, where he was pronounced dead.

Ernsting has been identified as a biomedical engineer who worked at the Ontario Institute for Cancer Research.

The victim, who was also an adjunct professor at Ryerson University, was out for his usual evening walk when he was approached by a man and fatally stabbed, police say.

Investigators believe the stabbing was the result of a botched robbery.

Calvin Michael Nimoh, 21, was arrested and charged with second-degree murder shortly after the incident.

Now, Nimoh has also been charged with robbery, assault with a weapon, and possession of a dangerous weapon in connection with an alleged stabbing and robbery that occurred approximately two hours before Ernsting was killed.

A 65-year-old woman was stabbed during a street robbery in the area of Yonge Street and Summerhill Avenue, police say.

On Thursday, two other people were charged in connection with the incident. Tia Thompson, 24, and a then-17-year-old girl who cannot be identified, have both been charged with robbery, aggravated assault and possession of property obtained by crime.

Thompson has also been charged with accessory to murder after the fact and obstructing a peace of officer in relation to Ernsting’s death.

None of the charges against any of the accused have been proven in court.