Marcel Petiot had a long history of helping himself to other people's things. His looting of his own army post might have been kind of funny, but when the horrors of WWII gripped France, his methods turned much, much darker. 

Sources:

Jenkins, John Philip. Marcel Petiot. Encyclopedia Britannica. Last accessed on December 9, 2019. https://www.britannica.com/biography/Marcel-Petiot 

Norman, Abby. Marcel Petiot May be the Most Despicable Serial Killer Ever. All That's Interesting. September 28, 2016. https://allthatsinteresting.com/marcel-petiot