* Teenager threatened to act during chatroom discussion
* Authorities look into whether his father should be charged
* Townspeople lay flowers, express shock
* Interior Minister says gun laws do not need tightening
(Releads with chatroom warning, adds colour, quotes)
By Nicola Leske
WINNENDEN, Germany, March 12 (Reuters) - A teenager who killed 15 people in a shooting rampage in Germany on Wednesday warned in a chatroom the night before that he planned to go to his former school with weapons and stage a "proper barbecue".
In a chatroom discussion with another 17-year-old in Bavaria on the eve of the shooting spree, Tim Kretschmer gave an explicit warning of his deadly plan, said Heribert Rech, interior minister of the state of Baden-Wuerttemberg.
"I’ve had enough," Rech quoted from the chatroom message.
"Always the same. Everybody’s laughing at me. No one sees my potential. I’m serious. I have weapons and I will go to my former school in the morning and have a proper barbecue. Maybe I’ll get away. Listen out. You will hear of me tomorrow. Remember the place’s name: Winnenden."
Rech told reporters that Kretschmer’s chatroom partner had not taken the message seriously at the time but had told his father after he saw reports of the shootings.
Kretschmer, described by neighbours as a loner with a fondness for violent videos, shot dead 12 people at his old school in the southern town of Winnenden and three more outside before turning the gun on himself when police cornered him.
Officials revealed on Thursday that Kretschmer had received psychiatric treatment for depression between April and September, before breaking off the sessions.
The motive for the attack remained unclear, although he seems to have targeted women. Eight of the nine students and all three of the teachers he killed in the school were female.
Investigators said on Thursday they had found pornographic pictures on his computer as well as violent video games.
GUNS FROM FATHER
Weeping students placed flowers, and candles at their school on Thursday, struggling to come to terms with a massacre that robbed them of classmates and teachers. [ID:nLC765877]
"I don’t know if I can stay at this school. Every time you enter, the memories come back," said student Christin Pluengel.
Kretschmer fired 112 rounds, 60 in the school, and had 109 unused rounds with him when his body was found.
German authorities are looking into whether to press charges against his father, a member of a shooting club who had 15 guns and 4,600 rounds of ammunition at home.
Kretschmer shot many of his victims in the head at close range with his father’s legally-registered 9-millimetre Beretta pistol.
The other 14 guns were locked in a gun-closet as required by German law but the Beretta was kept in the father’s bedroom, police said.
"Everything here points to negligence on the part of the father as far as the storage of this weapon is concerned," said police spokesman Ralf Michelfelder.
Stuttgart prosecutor Siegfried Mahler said the father could face legal action if it became clear he had violated the law in storing his guns and prosecuted for involuntary manslaughter if evidence arose that his son had given him warnings of his plans.
Germany toughened its gun laws in 2002 after 19-year-old Robert Steinhauser shot dead 16 people, mainly teachers, and himself at a high school in the eastern German city of Erfurt.
Interior Minister Wolfgang Schaeuble told Reuters in an interview on Thursday that he saw no need to tighten gun controls further after the shooting.
"We shouldn’t think about tougher laws all the time, but think about what we can change in society," he said, asking whether it was useful that Germany’s two main TV channels were showing boxing matches on Saturday evenings and criticising a rise in violent action films. (Additional reporting by Kerstin Gehmlich; writing by Noah Barkin and Madeline Chambers; editing by Philippa Fletcher)