The mayor said the statements of the man behind the bloody car crash near the site of the Islamic attack in Berlin were “incomprehensible”.

BERLIN (AP) — Investigators are trying to decipher the “confusing” statements of a man who deliberately drove a school group in Berlin in anger, the city’s mayor said on Thursday.

A woman, a school group teacher from central Germany, was killed and six people were fatally injured in an incident on a popular shopping street in the center of the capital on Wednesday. Three more people were seriously injured.

The driver, a 29-year-old German-Armenian living in Berlin, was immediately arrested after his car stopped in the window. Berlin Mayor Franziska Giffey said authorities determined Wednesday night that it was “a happy act of someone with a serious mental illness”.

He told public broadcaster RBB Inforadio that researchers are working to determine the context and how anything affects it. “They’re also trying it out with the help of a language mediator to learn more from the somewhat confusing claims he’s making,” he added.

Iris Spranger, Berlin’s top security official, said on Wednesday that posters of her “expressing her thoughts about Turkey” were found in the car. But she said it was “irresponsible.”

Giffey said officials are yet to know if the posters have any connection to Wednesday’s incident.

In 2016, a car collided with pedestrians near the scene of the attack after an Islamist extremist drove a stolen truck to the Christmas market, killing 13 people. Giffey said Wednesday’s crash “showed the deep wounds and trauma” associated with the incident.