- “Survival of the fittest. That's the rule in the Drop, the only rule. These numbskulls can't see the potential in leftover traces of Sports Boost, Armored Shell, the tonics for increasing muscle mass and density… but I see the king of the jungle.”
- ― Leo Hartwig[src]
Hartwig sought to create a new Gene Tonic formula, both as a means of self-defense and with the intention of selling his product. His formula consisted of Sports Boost and Armored Shell mixed together along with several other Tonics designed to increase muscle mass. He performed his first test on himself, and it turned him into one of the first Brute Splicers, roaming in Pauper's Drop. At some point after this he became a member of the Rapture Family, serving under Grace Holloway as a sort of enforcer.
- Main article: BioShock 2
Hartwig makes a brief appearance in Pauper's Drop at the Fishbowl Diner. He appears when the player is returning to the train car after confronting Grace, and will attack them in an ambush. He behaves like a regular Brute but has aid from a Turret and some Splicers, making him more difficult than other Brutes encountered so far. He is killed by the player in the heat of battle, and his only audio diary is found on his corpse.
- BioShock 2 Strategy Guide, page 121: "The Brute Splicer seen roaming about near the diner on the way out of Pauper's Drop is actually one of the scientists who worked on the Plasmid program for Sinclair Solutions. His name is Leo Hartwig and, well, you can see he didn't mind experimenting with his creations."
- Leo Hartwig's Audio Diary: Field Trial #1