What you're saying is half true, from the empirical evidence. Committing a first-time violent offence, and there's no other history of a violent offence, is actually associated with a decrease in the likelihood of it recurring. It may sound surprising, but a violent offence by itself with no history makes you less likely to commit a new violent offence.
Once you've gone by and started having a history or a pattern of violent behaviour, then the risk begins to increase. If you've committed a violent offence, and you've done it once before, yes, you have a higher likelihood. If you've done it twice before you have a higher likelihood, and those likelihoods increase in very small increments. Our prediction gets better when we start considering other risk factors.