Lenny works both for his father and occassionally with Mikhail Faustin. However, as his state of mind degrades, Mikhail believes that Lenny is betraying him and working with the police. Faustin commissions Niko Bellic to kill him as revenge. Upon confronting Niko, Lenny is shocked that Mikhail thinks that he's working with police, claiming that he is involved in deeper criminal acts than even Faustin can imagine. He then orders his bodyguards to dispose of Niko.
Bellic is able to outfight the bodyguards and chases Lenny through the subway station, gunning him down. His murder then sparks a miniwar between the Faustin Family and Petrovic Family, eventually leading up to Mikhail Faustin's execution.