They are "nymphs" (juvenile forms) of something. If there are a bunch of them, then they are probably not assassin bugs. It is a rule of ecosystems, that vegetarian animals (including the bugs that eat your garden) are much more numerous than the carnivorous predators that prey on them (including beneficial insect predators). It must be so, if wolves out numbered the rabbits and deer they eat, they would all starve to death and soon they would no longer out number their prey.
So assassin bugs tend to be found singly, while the similar looking leaf foot bugs (including squash bugs, stinkbugs and others) tend to be found in herds.
Here's a thread about identifying nymphs of assassin bugs and leaf foot bugs: viewtopic.php?f=39&t=54393&p=310738&hilit=assassin+bug#p310738
Here's a picture of a mama stinkbug guarding her babies (I didn't know they did that, insects generally aren't real loving mothers):http://www.brisbaneinsects.com/brisbane ... arent4.jpg
Trouble with ID'ing is that there are many different varieties, with different colors and markings AND they go through several different instars (moltings) that each look slightly different. Here's a picture from bugguide.net of tomato stinkbug juveniles:http://bugguide.net/images/cache/IZT/L0 ... MRULHZ.jpg