ROME -- A police officer is under investigation for possible manslaughter in the shooting death of a soccer fan that provoked riots across Italy, news reports said Monday.
Four people were detained for taking part in Sunday's violence in Rome, where angry fans attacked a police barracks near the stadium and the building hosting the Italian Olympic Committee.
Sports authorities met in Rome to decide on possible measures in the latest episode of unrest related to soccer. Last season, a policeman was killed in riots following a game between Catania and Palermo in Sicily. The killing prompted authorities to stiffen security measures in and around soccer stadiums, such as barring some fans from traveling to games.
Gabriele Sandri, a 26-year-old disc jockey from Rome, died after a bullet struck him in the neck while he sat in a car. Police said an officer fired shots to disperse a scuffle between soccer fans at a highway rest stop in Tuscany.
Police have called Sandri's death a "tragic error'' and the exact circumstances surrounding it remain unclear. But police chief Antonio Manganelli promised to shed light on the event.
"We'll uncover the truth,'' he said Monday.
Officials said the police officer who fired the shot was under investigation for possible manslaughter by magistrates in Arezzo, a Tuscan town about 125 miles north of Rome where the killing occurred.
"For now he is under investigation for manslaughter," Arezzo police chief Vincenzo Giacobbe said, adding that the charges could become more severe.
Initial reports widely diffused Sunday said police intervened to stop a scuffle between Sandri's group of Lazio fans -- headed to see their club play at Inter Milan -- and a group of Juventus fans.
But Giacobbe indicated Monday that the officer who shot Sandri may have not realized it was a fight between soccer fans.
"[The officer] intervened to calm down what appeared to be a fight,"' Giacobbe said. "He didn't know if they were fans. Another thing to clarify is why it was called a fight between fans. We think so, but [the officers on the scene] didn't know it. They saw with their own eyes that a fight was starting, and banging on a car.''
According to a police statement Sunday, an officer who had stopped his car on the other side of the highway fired two warning shots in the air. But the unidentified officer was quoted as saying by Corriere della Sera on Monday that the second shot went off accidentally.
Sandri's death forced the suspension of three Serie A matches as clashes erupted in cities including Milan and Bergamo in the north. Enraged by the shooting, rioters smashed windows and hurled stones at police cars.
In the Italian capital, violent fans rioted into the night, setting trash bins and police vans on fire. They attacked the police barracks near the Stadio Olimpico and raided the nearby Italian Olympic Committee headquarters.
About 40 police officers were injured, ANSA reported. The Italian Olympic Committee estimated the damages to its headquarters at about $147,000.
By morning, four people were detained in Rome, police said. ANSA said that they would be charged with vandalism and terrorism -- a charge added to ascertain possible ties of the rioters to neo-fascist groups.
No sanctions have been decided yet, but sports officials were holding a series of meetings involving the Italian soccer federation and the Olympic committee, amid calls of a halt to soccer.