"I'm sitting at Ball State and I see a young man, it looks like he's carrying a gun, walking toward the library." 

This 911 call started a 20-minute gun scare on Ball State's campus Wednesday. The call ended up being a false alarm, caused by a Humans vs. Zombies player carrying a Nerf rifle around. 

The woman who called said she only saw the man from behind, which could explain why she hadn't been able to tell if the gun was real or not. 

"I couldn't see the gun from the front, I saw him after he passed me," the woman said. "I saw him from the back of him."

The woman said she saw a man wearing all black walking toward Bracken Library, and kept asking for police to send someone to the area. 

"He was wearing something strapped around him," the woman said. 

The call lasted about four minutes, and toward the end, the woman seemed desperate to get away from the area. 

"I really want to get away from here, I just wanted to call someone because I didn't see any cops or anything," she said. "I'm leaving now, I was just staying to call." 

HOW IT ALL STARTED: Humans vs. Zombies player sparks gun scare on campus

Ball State issued the first emergency alert at at 2:09 p.m.: "A male suspect wearing all black with a green bandana has been sighted carrying a long rifle near Bracken Library and Woodworth Complex."

An all clear was issued about 20 minutes later, after police converged on a man in the lobby of the David Letterman Communication and Media Building. The man turned out to be an alumnus who had come to campus in combat gear to play Humans vs. Zombies, said junior Chinese major Brady Fisher, an organizer for the group. The man had a painted black Nerf blaster with an orange tip and was also wearing a skull mask — a guise Fisher said is typical for players.