Almost nothing is known about Dario other than that he wanted to be a novelist, however, due to his mother's influence, he resigned to his dream and became a salesman. He and his family were apparently not local residents of Raccoon City, as Dario was registered at the Apple Inn, suggesting he was in town on business.
During the evacuation of Raccoon City on September 24 when the town was consumed by an epidemic that turned most of the population into zombies, Dario and his family were forced to fend for themselves, attempting to escape the encroaching infected hordes through the ruined streets of Raccoon City without protection or chance of aid.
Some time during or after the collapse of the city on September 26, Dario's mother, wife and daughter were killed in the chaos. Being the lone survivor of his family, when Dario finally reached the safety of the warehouse, he was already a completely broken man. Some time later, Dario was found by another survivor, Jill Valentine, that suggested risking leaving the site for further safety, however, Dario furiously rebukes her, locking himself inside a shipping container in the deluded belief that it would be the safest option.
While inside the container, Dario wrote a memo where expressed his despair at believing that he would end up dying like his family and regretted that he failed to become a novelist. Eventually, he left the container, but, as Jill had alerted, the warehouse was not a secure location, as zombies managed to invade its interior who ending up cornering and devouring Dario when he tried to leave the place. Jill then found his body when she returned at warehouse.