Read the article. The message was pre-recorded. They expected the bomb to work, either that or it was a warning, which still strikes fear into many people’s hearts. IMO it was a warning due to the fact they(the perps)left the hazard lights on and the motor running which, of course, drew attention to the vehicle even before it caught on fire.
That was my initial reaction also - was the whole thing meant to be discovered - but everyone shook up as they have sent a signal they can do it - anytime... they are big on propaganda