The threat was deemed not credible after police searched the campus.
The reports ended up being about a fight involving parents and students off school grounds.
Authorities placed Poly High School on lockdown shortly after 3 p.m. Wednesday as police investigate an incident at or around the school.
Police quickly found the robber and a gun, ending the need for a lockdown moments after it was ordered, officials said.
Long Beach police have arrested a suspect threatening to blow up a vacant garage he barricaded himself in for multiple hours on Thursday in the city’s Los Cerritos neighborhood, authorities said.
A dispute between neighbors caused a middle school in Long Beach to go on lockdown Tuesday afternoon, Long Beach Police Department (LBPD) spokeswoman Megan Zabel said.
Edison Elementary School was placed in lockdown this afternoon, as Long Beach police assisted the U.S. Marshals in searching the area for a felony suspect wanted on a reported assault with a deadly weapon, officials said.