A gunman riding double on a motorcycle is the principal figure in a string of killings.
The similarity suggests either copycats or some type of organized effort.
The most recent attack started in Hatillo and resulted in a shootout with police in the San José barrio of Sagrada Familia. There a 32-year-old suspect identified by the last name of Monge died from police bullets.
Others were wounded in a misplaced effort at revenge.
Agents said that two men on a motorcycle shot and wounded a victim identified by the name of Castillo in Hatillo 6.
They fled, but friends of the victim took off in search of the gunmen but ended up intercepting an innocent motorcyclist.
He and a 10-year-old nearby were injured by bullets.
Meanwhile police chased the suspects into the southern San José barrio where the shootout took place. Two minors and a second suspect, 18, suffered wounds there.
Two persons on a motorcycle were identified as the suspect in a shooting Thursday in Miramar. A 49-year-old man identified by the last name of Ceciliano died.
Two persons on a motorcycle also were identified as suspects in the shooting of an expat businessman in Escazú Wednesday morning.
However, there still does not seem to be much support for a proposal by Francisco Segura, director of the Judicial Investigating Organization. He wants to forbid persons from riding double on the motorcycles. Motorcyclists object to this proposal and conducted a demonstration in San José Thursday to show their opinion.