EMBED >More News Videos Gun scare at Philadelphia school: Jeannette Reyes reports during Action News at Noon on May 31, 2018.

PHILADELPHIA (WPVI) -- A lockdown has been lifted and three students are in police custody, after a gun scare at a Philadelphia public school. But concerns remain.It all began around 9:50 a.m., shortly after classes started Thursday morning at the Tanner Duckrey School in North Philadelphia.A concerned mom called the school telling them that her gun was missing and her son, an eighth-grade student, might have taken it.That boy had already been suspended from this school for an unrelated incident.But Philadelphia police were concerned that he might come to the Duckrey School with that gun.So the building was placed on lockdown and police did a K-9 sweep.That is when they just happened to stumble upon a B.B. gun hidden in a backpack which belonged to another student, completely unrelated to the first incident.That 13-year-old student was taken into police custody and was being questioned."I know that we acted quickly once we heard of this report of a possible threat and we did a full search and we found it and confiscated it," said School District of Philadelphia Spokesperson Lee Whack.The missing gun was not found in the school building - neither was the 14 year old whose mother thought he might have taken it.He and another student, who allegedly handled that missing weapon, were taken into custody elsewhere.About an hour after the incident began the lockdown was finally lifted and parents let out a sigh of relief as they embraced their children.It was a scary morning for some of them, who had learned about the incident as it was unfolding, through calls and texts they received from their children.Parents rushed to Duckery, located at 15th and Diamond to retrieve their children.As the incident was unfolding, Felicia Pendleton's fourth-grade daughter text her mom that the school was on lockdown and her classmates were hiding."I asked her, I said, 'Is it a drill?' She said, 'No, something really happened and I am scared' so I just came straight up here," said Pendleton.Many parents expressed relieved that the incident was resolved peacefully and no one at the school was hurt.Officials said neither the boy who may have taken the gun from his mother nor his friend who allegedly handled the real gun ever set foot on school property Thursday.That weapon has not been found, but police said they are certain it is not at the school.A letter was sent home with students explaining what happened.------