The robbers escaped with cash from Shirl's Drive-In and were still being sought late Monday.
Robert W. Wilde, 18, and his 43-year-old manager were shot during the robbery. Both were rushed to Kenosha Medical Center, where Wilde was pronounced dead. The manager, who was not named by police, was treated and released from the hospital.
Kenosha police launched a wide search for the robbers with support from other law enforcement agencies, including a police helicopter from Illinois.
Police have not connected the incident to other robberies in the city this year, but detectives are checking with nearby jurisdictions, Kenosha police Sgt. Hugh Rafferty said. It was the third homicide in Kenosha this year, he said.
Wilde was a student at Indian Trail Academy, a high school on the city's west side, where he was enrolled in the biotechnology program, Principal Beth Ormseth said.
Ormseth said Wilde stood out because of his maturity and willingness to stand up for others. Ormseth recalled Wilde coming into her office to lobby for a schedule change - not for himself but for his friend.
"He was very loyal to his friends," she said. "He would be an advocate. He came into my office and said, 'My friend really needs these classes for what he is aspiring to do.' "
Wilde's family declined to talk with a reporter Monday. The owner of Shirl's, on the city's south side, did not return calls. He owns a second restaurant by the same name in Zion, Ill.
The restaurant's Web site had a message Monday night: "We are deeply saddened by the tragic loss of a cherished employee that was senselessly shot and killed Sunday. . . . Our deepest sympathy are with his family and girlfriend. We are devastated by this unnecessary tragedy."
The manager, Wilde and four other employees were preparing to close around 9:30 p.m. when the robbers barged through the back door, police said. One of the masked men had a gun, the other had a knife.
It was unclear from police exactly what happened next. Wilde and the manager were both shot, and the robbers took an undisclosed amount of money. The four other employees, females ages 17 to 20, were not harmed.
The manager called 911 and calmly said, "Shirl's Drive-In. There is an armed robbery going on right now. I have been shot in the back and I am bleeding," according to the 911 tape.
The manager said the robbers were still in the business and then said, "Goodbye." The dispatcher told him to stay on the line, and he passed the phone to one of the teenage females.
"Come. Please help," the girl said. She later said, "Where is my boyfriend?" It was unclear if she was talking about Wilde or another person at the restaurant.
During the tense, nearly five-minute call, the phone was passed around as the dispatcher solicited suspect information and gave instructions for medical care. The workers reported the robbers ran from the restaurant.
The manager was heard saying, "Rob is down! Rob is down outside!"
The teenage females were screaming, and the manager told them to lock the doors.
Robbers wore masks
Police reported that the robbers were Hispanic males, however both were masked. They were between 5 feet 10 inches and 6 feet tall. One had long hair, a tan parka, a blue shirt, camouflaged pants and a black mask, according to police. The other man had a red or brown parka or sweat shirt, a green shirt, tan shorts and a black mask, police said.