It's always worth contacting one of the agencies who deal with these things to talk things over. Small scale stealing is often a part of growing up. It may not mean that your child will become out of control but is learning what risks they're prepared to take. It's important that you ask your child these questions now - they may need your assistance in staying out of trouble. It's easy to forget how we all had to learn the limits of our behaviour and to control our anger.
Adolescents are particularly prone to outbursts of temper.
If needs be, you may have to apply sanctions such as stopping pocket money etc. However dealing with things as soon as possible after they happen will usually pay off. Love and support and, if necessary, sanctions are important. Remember that most children will grow out of it. Many children don't realise this or, indeed, appreciate that they are putting themselves at risk.