Remember the time Kieran and KP were married, and he had to look after the animals and the grounds. He said he was used to it because he had helped his granddad out on the farm.
If KH is from a family farming background then it isn't surprising that he would have a gun. Most farmers have them.
For all we know, this gun could have been safely stored and Kieran could be a responsible firearms user who follows safety advice.
'intent to cause fear of violence' - maybe KP knows he has the gun and made up a story that he'd threatened her, or she could have put J&B up to it.
There just isn't enough information here to make me think he's committed an offence. It says he is 'still in custody', we'll see how things go.