Sorry for the rough start! Thanks for the feedback and bug report.
You have to pick up the pistol, it might be hard to see. Then you need to hold the RMB/right stick to aim and then LMB/right shoulder button to fire. Did it not work that way?
The start button I have to fix. It's because I wanted to prevent accidental resetting of the save file, but the first start being long is very unintuitive (especially since the sound is also still missing). Will fix that tomorrow!