There is more than one article. You may have overlooked my reference to the Evening Times, or else not realised that the original link was to the BBC. Here's a link to the Evening Times. It's best to read as many diverse accounts as you can for events like this.

This article states, "Ali then shot at Goldie to chase him off but the convicted housebreaker then punched the step-father. Goldie then dropped a metal cosh and at this the accused fired a second pellet, hitting his target on the chest, the court was told."

It sounds like the first shot was to chase him off, and missed, and for the second shot he changed his aim and hit. It sounds like an escalation. It's easy to believe he was trying to do as much damage as he could. He may or may not have been aware that the gun wouldn't kill; at any rate, he's not pleaded guilty to murder, but it sounds like a serious assault on an unarmed man.