Investigators discovered the man's body on the ramp to an underground parking area of a building in the town on the Italian border on Thursday night, cantonal police said in an earlier statement.
After being shot, the man, a resident of Chiasso, was run over by a car entering the parking area, police said.
Within 48 hours Ticino police arrested five men in connection with the murder.
On the night of the shooting, a 26-year-old man with dual Brazilian and Italian nationality was arrested in his home.
The following day officers picked up a 26-year-old Swiss man, a 36-year-old Romanian man, a 29-year-old Kosovo man residing in Bellinzona and another 26-year-old Swiss man from Lugano.
On Tuesday, police said they detained a 32-year-old Swiss man who is suspected of aiding and abetting the alleged crime.
The investigation has been coordinated with police by prosecutor Pamela Pedretti.
All but one of the suspects are already known to law enforcement officials, who are tracking other individuals who may have knowledge of what happened on Thursday night.
According to the initial evidence, the murder appears to be a settling of scores in the drug trafficking world, the ATS news agency reported.