Police said officers arrested the boy, who was not identified, on a third-degree felony charge of making a terroristic threat.
The threat prompted managers of the Walmart at 1310 N. Texas Blvd. to close the store late Wednesday in an effort to protect its employees and customers, police said.
Officers responded to the store just before 11 p.m. Wednesday after 911 callers alerted authorities to a social media post making violent threats against the store. Officers secured the Walmart and spoke with store managers, who decided to close the store as a precaution as police investigated.
With the help of the FBI and the department's Facebook followers, police said they were able to identify the person behind the threats as a 13-year-old boy.
Police said they searched the boy's home and his family's vehicles and found no firearms.
"The Weslaco Police Department reminds the public, especially juveniles active on social media, that all threats will be investigated and taken seriously," police said Thursday in a news release. "There are consequences for these threats!"