Good Question, Other than fear and politics which Henry Taylor mentioned most surefire way is to set off an EMP, this can be done without Nukes, so only electrical equipment would be effected.
Everything would be disabled, most things these days permanently, that includes Ham Radios. then just blockade the roads, most people in the modern world don't see a massive power-cut and think "crikey, i need to get out of town immediately" and they are aware that power-cuts can happen. people would check with their neighbours maybe head down the street if nearby to the police station post office, hospital etc, as those places have generators to see if they can get some news, while the connections to the outside world wouldn't be all that effect, anything within the town that can use them would be inoperable so whether it be satelite radio microwave ham then only way of getting information would be from two sources
- Walking out of town (modern cars would be completely dead) and finding out from someone else outside of the effect area (all on potentially blockaded roads if you team has anything to do about it)
- From Preppers, those are the only people that would have equipment within faraday cages to protect them from EMPs, and lets be fair, when old crazy dave that alwasy talks about preparing for the end of the world as we know it starts saying the government has zapped the town to do x or y... who's really going to believe him. even normal people that are generally prepared and just might have a faraday cage still won't straight away think "the end is nigh watch out for government hit squads etc."
Especially if this happens in the evening it leaves the townspoeple with a couple of options left, head to bed early, after fumbling around hitting their heads on the cupboard door while trying to find some candles despite never hitting their heads on that door when not looking for candles! and see if its all back to normal in the morning
Or head down the pub, the pumps aren't electric, their gas pressurised, so they might be not quite as cold but its still beer right? or the beer is bottled and they can sit in a candlelit pub next to the barman with a bump on his head and be thankful that beer can stay cold for quite a while during a powercut.
Powercuts happen on average once a year where i'm from, so fair enough if the cars and phones stopped it would be strange but ignorance is bliss, and the Pub option is what i did last time there was a powercut at home, I don't know why my missus always puts the candles in that stupid cupboard
The Police would probably send someone on a pushbike to the next town over to find out whats going on, but by having someone in place to see where he heads and having the blockade grab and knock him out the town would be none the wiser