Half of this story is now being told - the intentional capture of Macho B by AZ Game and Fish. The other half of the story, which may be impossible to prove now (ironically due to Fish and Wildlife ordering the wrong kind of necropsy), is that the capture and associated stress, drugs, foot, and canine tooth damage led to the death of Macho B. The decision to euthanize Macho B may have been warranted by the time of re-capture.
Macho B had been in a foot snare for an unknown amount of time after initial capture, potentially many hours and obviously had foot damage. The tree to which he was chained was apparently severely scratched. Capture Myopathy, a condition which is caused by stress and sometimes over-exertion, often kills its victims in ways which fit Macho B's symptoms very well. All evidence and photos point to a very healthy Jaguar (esp. for his age of 16-20 years), which started a quick decline in health almost immediately after capture. See videos of Macho B after capture here.
Hopefully we all learn a lesson from this debacle for next time a jaguar decide to take up residence in our state