City officials don’t know who triggered Dallas’ outdoor warning sirens late Friday, but they do know how it was done — by broadcasting a few tones, via either radio or telephone signal.

In other words, there was no computer hack.

“It’s a radio system, not a computer issue,” Dallas City Manager T.C. Broadnax said Monday morning.

More details on the siren hack can be found here.

Photo Credit: Dallasnews.com