Kesean Williams was shot as he sat in his home on Wednesday night. (CBC)

The slaying of a nine-year-old boy — shot while inside his home — may be connected to previous tenants, police say.

"This was not a stray bullet," said Peel police Chief Jennifer Evans.

Kesean Williams was shot Wednesday night while sitting in the living room of a townhouse in Brampton, Ont., about 40 kilometres northwest of Toronto, where he lived with his mother and brother.

Peel Regional Police said Kesean was sitting with his 15-year-old brother when a bullet — probably a single shot — "came from outside the window." It struck the child in the head.

The emergency call came just after 10:45 p.m. Wednesday night. The townhouse complex where the shooting happened is at Ardglen Drive, near Kennedy Road South and Clarence Street in Brampton.

Kesean was rushed to Toronto's Hospital for Sick Children but died of his wounds.

Acting Supt. George Koekkoek told a news conference on Thursday afternoon that the family had only moved into the home last week and police suspect the residence was "targeted" — saying that whoever fired into the home may have been looking for the previous tenants.

Koekkoek said the circumstances "lead us to believe it was the house that was targeted." He said police were "exploring" the possibility the real target may have been the people who had just moved out.

"We're open to other things, but that's what we believe," he said.

Police stopped a taxi near the townhouse and three young men were taken into custody. Police later said they were treating the three as witnesses. No charges have been laid.

Koekkoek said officers are canvassing the neighbourhood looking for witnesses and obtaining security images.

"This is obviously heartbreaking when we have a victim of this age," said Rob Higgs, Peel Regional Police acting inspector. "We'll be putting all of our resources into finding the people responsible for this."

Police said the boy's mother was also in the house at the time and that the family is "devastated."

It's unfathomable," said Koekkoek, "that something as tragic as this could happen."

Kesean was a student at nearby Winston Churchill Public School. The school's flag was flying at half-mast on Thursday morning, and members of the Peel District School Board’s "critical incident response team" were providing counselling support, a letter sent to parents said.

Winston Churchill principal Kristin Bergen said in the letter that Kesean was a well-liked student.

"We have set up a memorial table in the foyer where anyone can go to write messages of remembrance and condolence," the letter said. "In the meantime, we will continue to support each other."

The young boy started attending Winston Churchill in September.