Unknown gunmen shot dead seven members of the same family, including three children, in an execution-style killing in their home in rural South Africa, police said Thursday.

A 5-year-old boy was among those killed in the shooting at a homestead in the eastern KwaZulu-Natal province late Wednesday, police said. The eldest victim was a woman aged about 55, they said.

The motive for the attack in the Highflats area, about 50 miles northwest of the coastal city of Durban, was not yet known.

“We are convinced as police that it was an execution. It was a planned murder,” provincial police commissioner Nhlanhla Mkhwanazi told reporters outside the house.

Some of the victims appeared to have been shot in the head while on the floor, he said. “There was a total of about 25 bullets that were used.”

The gunmen burst into the house as the family was watching television, officials said. They made one member of the family, who was outside the house, knock on the door and then opened fire once it was opened, police said.

“Police shall never rest until the person or people behind the mass shooting are arrested,” said Mkhwanazi, who urged anyone with information to contact the police.

South Africa has one of the highest peacetime per capita homicide rates in the world. Nearly 6,200 people were murdered in the country between April and June, according to police figures released in August.

Each day, 34 people are killed by guns in South Africa, according Gun Free South Africa, a nonprofit advocating for reduced gun violence.

In April, soccer star Luke Fleurs was gunned down as he refilled his car at a gas station in South Africa. Six suspects were arrested.

Last year, 10 members of the same family — including a 13-year-old — were killed in a mass shooting at their house in South Africa.