It was Burke who threw the tantrums, not Jonbenet. Jonbenet was becoming a little bratty and defiant, but as far as I know she didn't go into fits of anger. It was reported that a year after the murder, Burke threw a tantrum during band practice (if I recall correctly) where he threw his instrument on the ground and started crying.

A Ramsey friend, or former friend, said that Burke was an odd, quiet kid, but she loved him anyway. She said he had peculiarities like if he was talking to, say, Nedra and you walked up and tried to enter the conversation, that Burke would scream in your face something to the effect of "SHUT UP!!! I am not talking to you!!" Once again, this by itself doesn't prove anything, but it is interesting how quickly he could escalate with very little provocation. There were other things too that I can't talk about as they have never been in the media.