Veiled are known to have wild mood swings and their temperament varies animal to animal. My veiled for example, is extremely territorial and defensive. He will literally try to chase me out of his cage and recently gave me a nasty bite which I needed to have my finger glued to close the cut... Panthers, in my experience, are much more mild temperament wise.
All of the above is useless information if you do not take the time to build trust with your chameleon. Never grab at the cham, never approach the cham from above. Slowly work with the chameleon to get it used to you being around.
My girlfriend and I worked with my Veiled for months to build trust. He now absolutely hates me since I broke our trust by having to be the bad guy and give him oral meds daily when he had an infection. He still trusts my girlfriend and will practically come running to her and sit on her head when she is cleaning his cage...