The deputies were in camo from what I read in another article.
Joe Arpaio to militias: Beware or be shot - Associated Press - POLITICO.com
Sounds like a case of mistaken identity. The deputies flashed their lights and honked their horn a known drug runner method.
May I play the what if game..
The deputies pulled over, flashed the lights and honked the horn.
The Militia came out (in camo) and told them to freeze.
The deputies got out and (in camo - but with patches with ident)
The militia lowered their weapons and apologized.
The deputies arrested them because they knew they were cold meat if these were bad guys and were pissed.