Mr. DiPietro is a deceased resident of Vault 111.
DiPietro managed to secure a place in Vault 111 just before the bombs fell and became an occupant of one of the stasis pods. He died though from asphyxiation inside his pod, like most of the other vault dwellers. He is found next to Mrs. Whitfield and Mr. Whitfield.
Before the war, DiPietro was being approached by a chems dealer who lived in Sanctuary Hills at some point, stating that Mr. DiPietro was rather high strung, and that the dealer could fix that. This failed to make any headway however, leading to the dealer insinuating that Mr. DiPietro was self-medicating with pie on the dealer's terminal.
The monitor places him in stasis pod B1. On the floor right before his pod however, C9 is written in white paint. There is similar confusion for the rest of the pod occupants in this section. The pods in the other sections with the Sole Survivor (C1-C8) have been assigned correctly.
Mr. DiPietro appears only in Fallout 4.