Officials said a retired Marine Corps veteran, Andrew Koplin, stopped the carjacker with his concealed weapon.
The first incident involved an 80-year-old woman in a parking lot. The other attempted carjackings happened within a block of the first one.
The last two were stopped by Koplin, who said he noticed Montalvo pulling a knife in a Publix parking lot.
“He came right through here, kind of fast-paced walk, looking over his shoulder and I could see at first that he had the knife in his hand,” Koplin said.
Koplin said Montalvo got into a car with a young girl and held a knife to her throat.
Koplin was working around the corner and said he ran in front of traffic, got in front of the car and told him to get out.