Schwalmtal, Germany - A 71-year-old pensioner confessed to shootings late Tuesday in which three people were killed and a fourth wounded, German police said Wednesday.

The man, known for his aggressive behaviour, was due to be charged with the murder of two lawyers and a real estate appraiser visiting a house in the German town of Schwalmtal near the Dutch border, where the shootings took place.

A second real estate appraiser survived after managing to escape the house with two bullet wounds.

The pensioner was the father of a woman who jointly owned the house, apparently due to be sold by compulsory auction after years of wrangling over a divorce case.

The gunman said he wanted to punish those responsible for the protracted process of selling the house, which he had personally renovated and modified, "with a lot of muscle power."

Police said the man had a "very clear world view over what he considered to be law and order."

A neighbour, Anne Finke, happened to be at the garden fence as the briefly stepped out of the house. "I heard a bang - and suddenly the gunman was standing with the weapon just a few metres from me," the pensioner said.

"When the perpetrator came out, one person was already lying as if dead by the door, there was blood everywhere. Another ran out of the house with blood on his face," Finke added.

The gunman had arrived in town a day ahead of the valuation appointment, carrying a pistol and 100 bullets in his luggage. At Tuesday's visit he had started firing in the corridor without warning.

After emptying the gun's barrel, he reloaded it and fired three additional shots to make sure his victims were dead, said police director Juergen Schneider.

He subsequently hid the gun in the attic and surrendered, waving a white shirt from a window of the house. The 71-year-old later confessed to having planned the attack.

The daughter and the wife of the gunman, who had been present in the house, were being treated as suspects as they may have known of the man's plans, police added.

Both women had stayed in the house after the shooting, said state prosecutor Peter Aldenhoff. The daughter had alarmed the police from her mobile phone.

The daughter's ex-husband was absent from the viewing, where his lawyer had represented him, according to a friend and neighbour Daniel Bohlenz.

"Shortly after the deed he was here at the street corner and was relieved that he hadn't been in the house, because he thinks the attack was aimed at him," Bohlenz said.

The former husband reportedly said he had been warned before. "My ex-father-in-law had threatened me with murder several times," he told German daily Westdeutsche Zeitung.

The gunman had showed no regret during his police interrogation. "He thinks to have set a sign," the police said.

The pensioner had previously been charged with dangerous assault in 2006, for attacking two people with a baseball bat.(dpa)