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DALLAS (CBSDFW.COM) – The identity of who hacked the Dallas emergency siren system Friday evening remains a mystery, but city officials said they do know how it was done.

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Out of security concerns emergency management is keeping tight-lipped about how someone managed to hack the siren system, but after all 156 of the city’s sirens were set off, many are demanding answers and wanting assurance that this won’t happen again.

When Beth Mortenson and her family heard the siren across the street from their home blaring in the middle of the night, they weren’t sure what to do.

“It sounded like an air raid. I knew there wasn’t severe weather. Checked to see if there was severe weather. When there wasn’t I thought, we need to get out of here,” Mortenson said.

People across the city began flooding 911 operators with thousands of calls.

“I finally had got someone on the line for 911 in Dallas, and she said, ‘well we don’t know what’s going on,’ and I said ‘okay.’ I said, ‘well what does that mean?’ And she said, ‘we don’t know,'” Mortenson said.

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It took nearly two hours to shut down the system. A city spokesperson announced someone managed to hack into the emergency system and activate it, but officials are still working with the FCC to try to figure out who did it.

“We know how they did it, so we can stop it from happening again. Will we know who did it? I don’t know,” OEM Director Rocky Vaz said.

Dallas city councilman Philip Kingston says he’s skeptical about the hacking explanation and wants more answers from OEM when the city’s Public Safety Committee meets on Monday.

“Since the staff blamed T-Mobile for the 911 shutdown, and that turned out to be false, I really want to understand system vulnerability before we decide we’ve been hacked,” Kingston said.

City leaders agree it’s critical to restore the emergency system and the public’s faith in it.

“If it happens again, I don’t know, I might think twice about, ‘oh it’s just a malfunction,'” Mortenson said.

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The emergency management director said he hopes to have the siren system reactivated by the end of Sunday.