The fiend who mailed a bomb that detonated in a San Antonio FedEx store Tuesday also sent a second explosive from the same location — but it didn’t go off, according to officials.

Authorities located and secured the unexploded device at a different FedEx facility near Austin-Bergstrom International Airport, US Rep. Lloyd Doggett told the American-Statesman.

“They’re trying to figure out how to open the package without destroying it,” Doggett told the paper after being briefed on the investigation by federal officials.

The bomber sent both boxes from a FedEx store in the Austin suburb of Sunset Valley, Doggett said.

The one that exploded was likely headed for another location in Austin, authorities say — but ended up being routed via a facility near San Antonio, where it went off just after midnight Tuesday, leaving one worker with minor injuries.

The scare comes after four other explosive attacks in Austin this month — which have killed two people and injured four — and law enforcement officials said Tuesday they believe they’re all the work of a serial bomber.

“We do believe that these incidents are all related. That is because of the specific contents of these devices,” interim Austin Police Chief Brian Manley told the Austin City Council Tuesday, according to the Statesman.

Authorities have roped off the Sunset Valley store to the public, and FedEx says it had provided investigators with “extensive evidence” on the packages and the person who shipped them.