Police in southwestern Germany provided new details on Wednesday over a shooting in a university auditorium that left one woman dead and the idyllic city of Heidelberg reeling.

Officials from Mannheim, where the suspect lived, issued a statement clarifying that the man who opened fire in a University of Heidelberg lecture hall on Monday was an 18-year-old who purchased his weapons in Austria.

According to their initial investigation, the assailant, who killed himself before police could apprehend him, "bought a total of three long guns in Austria about a week before the crime."

Two of these weapons were secured at the scene along with around 150 rounds of ammunition. The third weapon, a rifle, was found by the Austrian police "in a room that the 18-year-old had rented during his stay," Mannheim police said.

They added that two of the weapons were bought from a dealer and the third from a private individual in Austria. Police had already said on Monday that the deceased suspect had no valid German weapons license.

The shooter arrived in Heidelberg from Mannheim via taxi, they said. He then entered the lecture hall, killing a 23-year-old woman and injuring four others before turning the gun on himself.

Police said that his motive remained uncertain, however, they were probing evidence that he had belonged to the neo-Nazi party "the Third Path" as well as indications he may have suffered from long-term mental illness.

In the statement, officials stressed the need to refrain from spreading misinformation and speculation, adding that his alleged involvement with  "the Third Path" ended in 2019 when he was still a minor. Police even said that some of the social media posts claiming to carry information on the shooter could form the basis of defamation cases and were also being looked at by investigators.

Combing through his social media profiles and confiscated devices had "so far not revealed any evidence of radicalization or of the alleged perpetrator having contacts with the right-wing spectrum," they said.

There is also no indication he had a personal relationship with any of the victims, according to their investigation.

Mannheim police said they were looking into whether crimes had been committed by other individuals related to the sale of the weapons, but that it could be difficult to prosecute because of differing laws in Austria and Germany.

Edited by: Mark Hallam