I really don't know what is going on Darlene, but I have had this sort of thing happen to me. Never found a cure.
If you are lucky, only the currently shriveled top will die, and the bottom will be fine. The bottom will ''seal off'' the top, and in a few weeks the top will be dry & brittle enough to just snap off. Use your diagonal cutters, and chop of the top, look at the stump, if the wood is discolored, cut lower. Cut to clean uniform wood, or normal wood for wood that naturally has a darker core. If the cause was mechanical damage as BNut suggested, the wood will be ''normal colored''. This is best case scenario.
IMPORTANT - clean your tools after cutting a diseased or suspected diseased tree. A wipe down with 70% or 90% rubbing alcohol (isopropanol) will effectively kill most bacteria, molds, fungi and to some extent virus. 70% works as well as 90%, less than 70% does not work as well. Ethanol, Methanol, or Isopropanol (Isopropyl alcohol) will all work for this use. Denatured ethanol is fine also. 190 proof white lightning will also work, but why waste it, drink it instead. I'm joking of course, you should not try to drink 190 proof ethanol, always water down to around 80 to 90 proof. Key is to clean tools. As a routine matter, if one were really conscientious, clean tools between trees, every time you move to a different tree, all tools used get a wipe down. There are other cleaning solutions, a few work better than alcohol, many don't work as well as alcohol. When I find the reference I am thinking of I'll post the list.
Back to what is wrong.
More likely, it is one of the catastrophic water molds, like Pythium, Phytophthora, Erwinia, or any of a dozen other plagues. In which case the symptoms will spread through the rest of the tree. These are extremely difficult to cure, I've never been successful. Purple discoloration is typical of Phytophthora, I believe Erwinia can be diagnosed by foul smell, at some point they all cause generally similar damage. They are traveling through the Cambium, just under the bark and the shrivelled look is the collapse of the cambium tissue as it is being digested by the pathogen. The discoloration of the wood when cut in cross section can also be a ring of purple, the purple or brown being where the normally green cambium should be. If the shriveled areas ooze sap when you touch it, what ever you do wash your hands before touching a healthy, unaffected tree. That sap will be loaded with spores (or the asexual reproductive structures that are a different name than spores, but I forgot the name).
If this is the case, the best you can do is prevent the spread to other trees. Move this tree so that no water from it splashes onto any neighboring tree, and no water dripping from it can drip down onto another tree. Without a definative identification, it is not advisable to go wild spraying different fungicides, because you don't know if it is a fungus or a bacteria, what kills one, will not kill the other. So just removing the diseased plant to a position away from the clean plants should be enough. Especially since this seems to be the only one affected.
Quince, flowering quince and chinese quince will get one of the ''cedar - apple type rusts'',, there are at least 2 different rust fungi that can use quince as the alternate host with juniper being the other host. The spores move around in early spring, that could be what got the top. It will form gummy oozing blobs of resin as soon as weather warms up a bit. These blobs of resin are loaded with spores and rain splash, or birds or other creatures by contacting the blobs of resin, will spread spores to neighboring junipers. This one will kill the whole branch it infected, but often the tree's own resistance will stop it from spreading lower. Observe what happens, that will help with the diagnosis.