Ciro Esposito’s condition deteriorated unexpectedly after a lung operation on June 19th, Italian media reported.
He had been in intensive care in Rome’s Policlinico Gemelli hospital since being shot ahead of the Italian Cup final between Fiorentina and Napoli on May 3rd.
Daniele De Santis, a 48-year-old AS Roma fan, is currently being held on charges of attempted murder.
Enzo, Esposito's uncle, was quoted in La Repubblica as saying he wanted justice for his nephew but also appealed for calm in light of potential threats of revenge from Napoli supporters.
"We don't want anymore violence, just respect for Ciro," he said.
A well known hardline ‘Ultra’, an organised group behind much of the violence surrounding Italian football, De Santis is also accused of shooting two other Napoli fans before the game, which was delayed by 45 minutes.
Reports following the attack suggested De Santis, nicknamed Gastone, provoked the group with smoke bombs, and when they responded badly he pulled out a gun and started shooting.
Hardline Napoli supporters have pledged to get revenge against the “Roman bastard” who shot Ciro Esposito.
They said the person responsible for shooting Esposito “would pay, sooner or later”, according to reports in May.
The violent attack is one of the worst seen in Italian football, but some say the authorities, despite pledges, have never really tackled the problem of hooligans.
“Soccer has long been a free zone, with no law, or rather without the state’s law — that of criminals and thugs has its full jurisdiction,” Maurizio Crosetti, a sports journalist, wrote in La Repubblica in May.