Maybe detectives could explain?

At a high school outside Houston

HOUSTON -- A northeast Harris County high school was placed on lockdown after a threat was phoned in, KPRC Local 2 reported Tuesday.

Sheldon Independent School District officials said the call turned out to be a prank.

No one was allowed in or out of C.E. King High School during the lockdown.

Harris County Precinct 3 deputy constables were at the school to provide extra security.

Investigators searched the school and did not find anything.

Detectives are working to determine who made the call and why.

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Maybe detectives could determine what the intended purpose of a school lockdown is? Who is it supposed to protect? How does it protect them?