Police on Tuesday arrested two half-brothers suspected of beating to death 20-year-old Emanuele Morganti after a row at a club in Altatri, south of Rome.
Mario Castagnacci, 27, and Paolo Palmisani, 20, are being held in Rome's Regina Coeli jail over Morganti's murder and there is "grave evidence" against both men, the chief prosecutor in the town of Frosinone, Giuseppe De Falco, told journalists.
"This case is shockingly serious because for trivial motives - an argument over a drink - an innocent and respectable young man lost his life," De Falco said.
A total of seven people including a father and son and an Albanian are under investigation after they were linked to Morganti's killing by eyewitness testimonies and security camera footage.
Castagnacci and Palmisani were arrested at the home of relatives in Rome, where they fled after the savage attack against Morganti early on Saturday when bouncers forced him to leave the Miro nightclub.
"Once he was outside the club, he was attacked several times by several people in different places - attacks that took place with different methods and levels of intensity," said De Falco.
"After the first attack, Emanuele tried to get away and he was followed. "Then he returned to get his girlfriend and he was attacked again."
Morganti was repeatedly kicked and punched and was left with a brain haemorrhage and multiple skull fractures after his attackers hit him over the head with an iron bar, spanner and truncheon, according to prosecutors.
Morganti was air-lifted to Rome's Policlinico Umberto I hospital in a critical condition and died there on Sunday from his injuries.
