[twyn1]

There was no secondary explosion after they detonated the first package (a backpack ??) -- still not sure what it was

[Deguello]

"There was no secondary explosion after they detonated "

According to a NYPD Bomb Squad guy on Fox this morning, detonating a device does not have to blow up the main charge but hopefully the ignition source for the device. Most of the time it is the crude devices that will detonate with the Bomb Squad's external charge.