CBS 5's red box of terror alerts us to the following: "San Francisco police have just arrested 3 people near Bret Harte Elementary School at 1035 Gilman Ave. after responding to a report of a person with a gun. No further details are immediately available."

Update: SFist talked to a school official -- who asked to remain anonymous -- who told us, "There was an incident, though we don't know too much about it." According to the school employee, the security guard "captured a suspect in their yard," explaining that the "all the children are safe." The school was on lockdown as soon as the suspect was spotted on campus.

Our source also told us that "the school security guard did a great job" in capturing the suspect right away/ They went on to tell us, "Unfortunately, this isn't the first time this [kind of thing] has happened."