There is a war being waged, a mutli faceted conflict between cyclists and motorists and cyclists and pedestrians. Cyclists unfortunately are widely despised by pretty much all other road, trail and footpath users, and even more unfortunately it's for good reason.
Some cyclists are complete c*nts, and we all know it, whether they are ignoring the highway code and mounting pavements or jumping red lights that they feel don't apply to them, or tearing down popular walkways at breakneck speed with scant regard for walkers, often elderly, sometimes small children and any dogs that they may have with them.
Of course it's only a minority of cyclists who are absolute bastards and hooligans, but those are the only types of cyclist everyone else notices, and my feelings are that some cyclist or other has enraged a hiker to the point where he has been driven to madness and now wishes cyclists severe physical harm and even death.
It's not just hooligan bicyclists, but some motorcyclists and e-bikers too that are responsible for dragging all of us into this ongoing conflict. Of course I'm not condoning the cowardly psychotic behaviour in the OP, but it probably began with someone on two wheels behaving like a prat.