I first stumbled across Theodore Gardelle on historyorb.com. I later found out that while he created art, he also murdered someone.
This link has one of his miniature paintings.
So, beyond this, we know little about Gardelle as a person before he committed this heinous crime. What kind of family did he have? Did he have lovers? What groups did he hang out in? Or did he keep to himself? Did he receive any type of training? Did he murder anyone else?
ETA: I found a biography on the painter. Haven’t read it yet.
Art History Ramblings 
What a bizarre story! I’ve never heard of Gardelle before. I wonder what success he met as an artist.
Another big mystery right there.