A couple from NSW allegedly planted a bomb under a car as part of a intimidation campaign against a driver who "beeped" at them in a McDonald's car park.
The man, 33, and woman, 31, were arrested in the Illawarra on Tuesday before police uncovered a pipe bomb, drone and baton.
Police allege the pair were left aggrieved after a driver tooted their horn at the woman when she was driving in a Warrawong car park - near Port Kembla - on February 22.
The woman then allegedly followed the car, recorded the number plate and tried to file a complaint with police.
But police allege the couple then took matters into their own hands, with an online harassment and intimidation campaign including death threats.
The escalating campaign ultimately led to the placement of a "sophisticated" improvised explosive device under the victim's car in nearby Koonawarra on March 5.
"This was an act of grievance-fuelled violence," Detective Superintendent Michael McLean told reporters in Sydney.
"The (initial) interaction was quite a benign one ... and from that, continued this behaviour that clearly is not something which is acceptable and became quite a dangerous series of events."
The victim was not known to the offenders and the work done to identify them was "ingenious" and indicated a specific intent, Det Supt McLean said.
He said the car targeted in the bombing was not destroyed, but the blast had the potential to seriously injure or even kill a person.
During their investigation, police discovered the alleged male attacker was also threatening another store worker over an unrelated feud.
The man was refused police bail on Tuesday on at least 10 charges including placing an explosive in or near a car with intent to cause harm.
He's due to face Wollongong Local Court on Wednesday.
His partner is expected to face the same court on May 22 after she was granted strict conditional bail on two charges including stalking.
The Fixated Persons Investigations Unit - a specialist squad set up in 2017 to target potential would-be terrorists or lone actors - helped investigate the pair.
