Can anyone in IL, or elsewhere, report more on the head-job of The Engineer:

I don't know beans about it, but I've never let that stop me before.

Any crypto used to authenticate the target for the boombox, or to obscure links to the assassin?

How was the blast specifically targeted at him and not a phone borrower?

How it was set off -- by user-dialing, remote control, some other means?

Try this scenario. Bomb in cell phone's trigger is activated by a tone, say the DTMF tones for the numbers 8 and 6. Assassin calls phone number, and performs the following authentication protocol: "Hi, this is J.Random Assassin. May I speak to Mr. Intended Victim Please?" "Speaking." "Message for youuuuuuuuuuu...." Beep Boop BOOM!!!