A 12-year-old Chicago boy allegedly held up an 11-year-old using a weapon that turned out to be a replica gun, police said.

The robbery occurred at the end of the school day on the campus of Palmer Elementary School in the North Mayfair neighborhood, police sources told CBS 2′s Chris Martinez.

Police were alerted to the incident after the 11-year-old victim and some of his friends later scuffled with the suspect to get the stolen money back. During that second confrontation, what looked like bullets fell from the suspect’s backpack. The ammunition was turned over to the school resource officer.

Chicago Police Department SWAT team members and K-9 units secured the school grounds late Friday afternoon and conducted a search. Police tell CBS 2′s Pamela Jones they found a realistic-looking replica gun.

“Nobody got hurt, all of the people were basically gone from the school,” Chicago Police Cmdr. Jose Ramirez said. “I’m satisfied with the conclusion. The officers did a great job.”

Police were talking with the suspect and his parents after the alleged incident. The boy could face armed robbery charges.

“Chicago Public Schools does not tolerate the presence of any weapon of any kind on school property for the safety and security of our schools, students, staff and visitors,” CPS officials said in a written statement. “School officials took the appropriate steps of notifying CPD, who then took immediate action at the school.”