Police said Dipina turned himself in several hours after the incident.
In an arrest affidavit, investigators said Scott Franklin, 41, had followed another vehicle to the intersection of 5th Ave. S and 6th St. Both vehicles were stopped at the red light, the affidavit said.
Police said Franklin was "yelling," "cursing" and acting out aggressively and got out of his vehicle, approaching the other car.
In the arrest affidavit, Dipina told police he didn't know what Franklin had planned, and so he pulled out a Glock 23, 40 caliber handgun out of his right pants pocket. He then shot Franklin as many as five times, the report states.
"Had he not gotten out of the car, he probably would still be alive," said Rick Shaw, with St. Pete Police.
Investigators said the crime was captured on surveillance video.
ABC Action News reached out to the state attorney's office to see if Dipina's charges may be upgraded, and they said it is still too early to know.
Franklin’s family tells ABC Action News they are devastated and are hoping for justice. They describe Franklin as the life of the party and a karate enthusiast. Services are planned for Thursday, May 5.