Gelding and Foal Problems

A friend has a gelding, mare and now foal. The gelding is behaving with extreme jealousy towards the baby. They had been pastured together for a week with no problems, then out of the blue, when mom and dad weren't home, the gelding attempted to kill the baby. Had the neighbors not been around he may have succeeded. We can seperate, but are afraid of the consequences down the road between the colt and gelding if they do not learn to cohabit at an early stage. The gelding also had a diseased testicle when he was gelded and we are wondering if his pituitary galnd may be affecting some of this stallion like behavior. Any suggestions would be greatly appreciated. Thanks