Some of us have more than 1 child. And we would know very well that the older child often gets jealous of his/her little brother/sister.
It can get very worrying sometimes, especially when the older child tries to hurt the younger sibling. Be assured that this is not uncommon. What you can do to help is to make sure that you react firmly, showing that what the older child is doing is wrong - but at the same time, encouraging the child to become more involved with taking care of baby.
Always be calm and controlled and do not scream at or provoke your child when he misbehaves out of jealousy. Otherwise, he might become more resentful.
Most importantly, remember not to leave a young child unsupervised with your baby. The child won't have a sense of the extent of damage he or she can inflict, and should therefore be supervised when handling baby.