One possibility (not claiming this is how it worked...) Buys cheap throw away cell phone, wires to bomb. Goes in Stadium and leaves vest, backpack, etc.
Goes outside and calls it.
But before he gets in, while arming it, the cell phone gets a call, or he pushes a button accidently on it, causing the speaker to sound (the easiest circuit to tap for trigger pulse is the cellphone ringer and/or speaker).
Tinfoil hats say that there are cell phone blockers in stadiums, but if there are they sure don't block outbound calls. Although I've had my cellphone take a message instead of ring while sitting in a ballpark, I assumed it was just cuz of excess circuit use in the ballpark. You sure see enough people on cell phones in ballparks.
Ok, I'll get back on my meds now...
Could be. My cell phone chirps when I lose coverage, then it returns.
Yeah.....I've been wondering if/why a SUICIDAL person would do themselves in and leave all those valuable explosives untouched in his apartment.
I read somewhere that one of the warning signs of a suicidal person is that, in addition to the other signs, they start giving their possessions away.