ALFRED - Students, faculty and staff on an upstate New York college campus were directed to stay inside for about two hours Tuesday until police found a young man seen carrying a gun and determined the gun was a toy.

Authorities said the student was involved in a game called Zombies vs. Humans on the campus of Alfred University, spokeswoman Sue Goetschius said.

“I don't understand it but it involves Nerf guns,” Goetschius said. The colorful plastic toy guns shoot soft foam darts or balls.

A staff member reported the possible gunman about 3:30 p.m. and positively identified the student when he was located.

An alert on the Southern Tier school's Web site at 3:33 p.m. said police were investigating a report of a man, possibly carrying a gun, who was wearing a green hooded sweat shirt and carrying a backpack. A 4:04 p.m. update said the search was continuing and advised students, faculty and staff against going outside until further notice.

The all-clear was given at 5:43 p.m., ending a building-by-building search on the 232-acre campus, about 80 miles south of Rochester in Allegany County.

“We had a credible report of a student with a gun,” Goetschius said. “We had to treat it seriously and we did.”

Zombies vs. Humans is described as a heightened game of tag played over a period of days on college campuses using toy guns to tag competitors.

“We've been here for a couple of hours, with police going around every place, so it's clearly an issue, particularly in the environment that we're currently in today,” William LaCourse, a professor of glass science, said shortly before the lockdown was lifted. “So, we're taking it very seriously. But from what I've learned, it apparently is a false alarm.”