Diamond Bar High School was put on lockdown Monday morning after the Los Angeles County Sheriff's Department notified the school of a "suspicious individual in the vicinity," according to a message Principal Catherine Real posted on the school's website.
The lockdown took place at around 9:45 a.m. and lasted to approximately 10:05 a.m., when the man in question was detained and in police custody, Real said in the post.
The Los Angeles Times reported that the threat to schools was the second in the area in the past few days. The first one happened Thursday when a 14-year-old student at Canyon View Junior High School in San Dimas threatened to bring a gun to the campus and kill a teacher, Sheriff's spokesman Steve Whitmore said to the newspaper.
During Monday morning's incident at Diamond Bar High, a man carrying a duffel bag and reportedly acting suspiciously, prompted the lockdown, Whitmore said. Deputies found out that the man, who at first appeared to be a transient, was a Diamond Bar resident and not a threat, Whitmore told the newspaper. The school was re-opened shortly after it was locked.
Police departments and schools have been on high alert since Friday's mass shooting at Sandy Hook Elementary School in Newtown, Conn.
Real posted a message, which included a link to the newspaper's story.
"The all-clear was given. We are back to our normal bell schedule," Real wrote. "Please know that your child's safety is our number one priority and once that safety was secured and verified, parents were notified as quickly as possible."