Some kind of monster crab spider. He tried to make lunch out of that little bug but it wandered away not knowing how close to death it had come.
Xysticus is a genus of crab spiders. Xysticus and Coriarachne are the dark brown or reddish-brown crab spiders often encountered on weeds or trees. While similar to the flower spiders, they tend to have shorter, sturdier legs and more patterned abdomens. They move slowly, and tend to hunt by stationing themselves in a high-traffic area and grabbing whatever arthropod passes close enough.