Police responded to a fight on Howard Street, one block from the beachfront promenade, and found Loftus bleeding from stab wounds in his chest and abdomen about 11:25 p.m. Monday.
Paramedics rushed him to Burdette Tomlin Memorial Hospital in Cape May Court House, but he died en route.
James Rybicki, chief of county detectives, said the slaying had occurred during "some sort of beef between two groups of kids" who did not know each other.
"They were mouthing off at each other," he said. "We're still sorting it out."
The suspect was held at the Cumberland County Juvenile Detention Center in Bridgeton. A probable-cause hearing was scheduled for Friday in Cape May County Juvenile Family Court.
The victim's father, James Loftus, said his son and two friends had been in Cape May doing what teenagers usually do in a Shore town on a summer night - looking for a good time.
He said that Cape May police would not tell him much and that he suspected officials were concerned about the impact of a street killing during one of the resort's busiest weeks of the year.
"It's a shocker where it happened," Loftus said, adding that officials could not tell him the last time there was a homicide in Cape May.
Arlene Harris, who manages a motel on Howard Street, said some of her guests had come upon the scene on their way back to their rooms.
"They were pretty upset," she said. "The area we're in is very quiet usually."
Loftus said his son had graduated from high school two weeks ago and planned to study law enforcement at Johnson and Wales University in Providence, R.I., in September. Christopher Loftus was well liked and enjoyed bodyboarding and surfing, his father said.
"This whole thing makes no sense whatsoever," he said. "My son's a pretty easygoing kid. He's not a fighter."
Loftus said he and his wife, Kay, had moved with their son and older daughter to Lower Township from Philadelphia in 1990, "ironically enough, to get away from this sort of thing."
"It's a terrible, terrible loss," Loftus said. "I will miss him very much."
A Funeral Mass was scheduled for 11 a.m. Saturday at St. John of God Roman Catholic Church in North Cape May.
Joseph Gambardello's e-mail is firstname.lastname@example.org.