Notorious German graffiti artist Walter Josef Fischer, better known as Oz, was found dead on the tracks of Hamburg’s subway system after being hit by a train late on Thursday night, the Guardian reported. Police discovered a freshly painted mural and a can of spray paint next to the 64-year-old’s body.

Born in Heidelberg, Fischer worked as a gardener during stints of homelessness. He moved to Hamburg in the early 1990s and gained prominence as a notorious graffitist. It is estimated that he painted over 120,000 tags throughout Germany, so many that Police initially suspected a gang of vandals was behind his work.

His signature tags consist of spirals, smiley faces, and his chosen name. They split popular opinion in Hamburg, Germany’s second largest city. Some residents viewed the tags as vandalism. Others appreciated the lighthearted murals as art that brightened up the rainy, northern city.

Fischer’s graffiti invariably led to encounters with law enforcement and expensive legal troubles. He spent a total of eight years in prison for damage of property and often reoffended only hours after being released. In 2012, he avoided jail after agreeing to pay a €1,200 ($1,500) fine.

Despite years of compulsive tagging, he denied being obsessed, telling a local graffiti magazine: “What does obsessive mean? I always tell myself there is a lot to be done. I don’t feel guilty for prettifying our environment.”