Eislingen, Germany - Police were Saturday questioning an 18-year-old in the slaying of his parents and two sisters at the family home Eislingen, south-west Germany. A police spokesman said the youth and his friend, aged 19, were being treated as prime suspects in Friday's shootings.

"The circumstances indicate it was somebody who had close links to the family or was a family member," said police spokesman Rudi Bauer.

The son told police he found the victims when he returned home on Friday morning after spending the night with a friend. The father, 57, mother, 55, and two sisters aged 24 and 22, were in different rooms of the apartment.

"All the corpses had gunshot wounds," the police spokesman said. "There were no traces of a break-in. The flat was not ransacked"

The son was a member of a local marksmen's club, according to police, who were still searching for the murder weapon on Saturday.

Police have been questioning the teenager for two days, along with friends and acquaintances of the family.

"Basically, we are concentrating on everyone closely connected with the family," said another police spokesman.

The father practiced alternative medicine in the basement of the apartment building, which was owned by the family. The mother was a teacher. The two daughters were studying to be teachers.

Three other families who live in the building said they did not hear any shots.

The killing comes three days after a man opened fire in a court in Bavaria, killing his sister-in-law and injuring two other people before turning his gun on himself.

That shooting happened less than a month after a teenager went on the rampage in and around his former school in Winnenden, south-west Germany, killing 15 people. (dpa)