I have a question about a felony charge from 18 or 19 years ago.

What if someone had a charge from 1995 of possession of marijuana with intent to sell. They haven't been in any trouble since. He did an inactive sentence and 36 months probation. It has been 18 or 19 years ago. Now this just happen, the person shot a registered gun of someone that stopped by his house and it was reported to the police that shots was fired came from his residence. The person told police he shot one time trying it out and he didn't have it in his possession. It was back in the person car with safety on. The person got charged with possession of firearm because of his felony from 1995. What could the worst case scenario be. Could he be charged with felony again or jail time?