A rolling wave of death that travels over all media, land and water is fairly difficult to conceive, especially if it does not propagate vertically as well as horizontally. If it travels at the speed of sound, would sound proof/ airtight, rooms/bunkers/vehicles be unaffected or at least weaken the effects? Short term coma or just getting knocked out, instead of dead?
At the speed of sound at sea level, it'll take about 16 hours to cover the globe. Assuming that death is instantaneous, there will be nobody left to raise the alarm, i.e., by the time you notice what's going on, you're already dead. The only warning people will get is that telecommunications become unresponsive, since there's nobody on the other end.
The survivors will be the inhabitants of: https://en.wikipedia.org/wiki/List_of_buildings_with_100_floors_or_more; and people currently on aircraft above 1000ft and people living in the Alps, the Andes (central S. America, in general), some of central America, the Himalayan foothills, some parts of China, and in the Ural mountains, off the top of my head.
Most of these people will die within the week, as corpses begin to fester and breed disease. If the wave affects animals as well, then most mammals, at least, probably also fish and reptiles, will die as well, adding to the mess. The knock on effects on the environment will kill most of them anyway, as the wind and rain washes the rotten bodies downstream.
People dependent on modern infrastructure will be severely affected, as there will be nobody left to maintain them; those communities that still aren't so dependent will carry business on as usual, for the moment.
By rule of thumb, 1 kg of biomass gives 1 mol of methane. Let's say 6 billion dead, 70 kg on average, gives 10^13 litres of methane at room temperature/1atm. Global warming effects aside, methane is slightly heavier than air, so will not easily dispersed in enclosed spaces, like cities, which is where most bodies will be. Cities, therefore, will be a fire hazard until sparks from unattended fires, electrical equipment etc., burn them down. Hopefully, this will deal with most of the the water pollution and disease issues.
Nuclear power plants, chemical factories,etc., are the next source of concern, along with nuclear and chemical arsenals. Depending on how the safeties are set up, unattended, these systems will force an automatic shut down. Otherwise, with no load to supply, the plants will explode; the nuclear arsenals will assume a decapitating strike and launch at preassigned targets, at best irradiate everything within their blast radius, at worst rupture the Earth's core.
In any case, the sensible thing for the isolated survivors to do would be to stay where they are, for the next few decades or so; afterwards, it depends on the survivors' technical expertise and what's left.