TORONTO -- An unarmed woman was killed in a drive-by shooting in north Toronto early Sunday morning while on her way home from a funeral, police said.

Toronto police Chief Mark Saunders told a news conference that the incident -- the fourth homicide in the city in 24 hours and 47th so far this year -- is indicative of a "street gang subculture" that has become an ongoing issue for officers.

Video footage released by police shows a silver SUV circling a neighbourhood before passing a vehicle and slowing down. According to investigators, a passenger in the SUV fired a single shot.

Jenas Nyarko, a 31-year-old woman sitting in the back seat of the second vehicle, was struck and killed.

Investigators said the vehicle drove away, firing several other shots on its way. They did not release any suspect information.

"To have an individual shoot at a vehicle that is practically full of occupants and then to drive away nonchalantly is a huge indication that they're the person that we're looking for," Saunders said. "They need to know that we're going to do whatever we can to apprehend them and do whatever we can to apprehend them."

Det. David Dickinson of the force's homicide squad said there's nothing in Nyarko's past to suggest she would have been targeted by the shooter, nor is there anything to suggest the three other people in the vehicle with her might have been targets.

Originally from Ghana, Nyarko moved to Canada in 2001 and worked at a shelter, Dickinson said.

"She was with three other friends. They were just returning from a funeral ... when she was shot," he said.

"It would appear that this is a case of individuals coming from one neighbourhood of the city to another neighbourhood and shooting the first residents that they see."

Investigators said there's nothing at this point to suggest this homicide and three others over the weekend -- two people shot to death in the city's west end early Sunday, and a man killed in northern Toronto a day earlier -- were connected.

"Any life is a concern for me," Saunders said. "Any time anybody shoots a gun inside this city is a concern for me."

He noted that on average there have been five more shootings per month this year than last, with an average of one more person shot each month in 2018 than 2017.

"That is not catastrophic, but I still don't like those numbers," he said.

Meanwhile, Toronto Mayor John Tory told reporters Sunday at the Pride Parade that the police service has the full support of the city.

"I think the police and myself are responding with a sense of urgency and I can just tell you right now, I've talked to the police chief today and they are applying every ounce of effort and intelligence and resources they have to taking these people off the street," Tory said.

"(The perpetrators) are thugs. They are people that I have no use for and we have got to get them off the streets, and the police are doing that."

Investigators said an autopsy will be conducted Monday and are asking anyone with information about the shooting to contact police.