The shootout at the cemetery in Figueres took place on Saturday, or All Souls' Day, a religious festival which sees Catholics visiting the graves of their dead relatives.
Hundreds of people were laying flowers on graves when shots rang out around midday.
Among the shocked witnesses was Marta Felip, the mayor of the Catalan town where Salvador Dali was born.
"We heard shots and shouting, and then people started to run," said Felip who had been taking part in the annual laying of wreaths to remember the victims of Spain's 40-year Spanish dictatorship.
There were "four of five shots" the mayor specified.
One of those ended with the life of a 30-year-old Roma man from the southern French town of Gavarre.
Within hours, police had arrested the shooter, also a Gitano, or a member of Spain's Roma community, Spain's El País newspaper reported.
Two other members of his family, a man and a woman, were also arrested for illegal possession of a firearm.
The incident also saw police calling for special reinforcements from Barcelona with authorities fearing possible reprisal attacks in Figueres' Gitano neighbourhood.
On Sunday, police sat down the two clans to try and broker a piece.
Initial reports suggest the dead man and his assailant had been expelled from the cemetery by their respective clans after an argument.
Once outside, one man fired on the other.
The three people arrested by police are currently in custody and will appear before a judge shortly.