Captain America is shot and killed

In the ongoing Civil War in the Marvel Universe over the Super Hero Registration Act an assassin has just killed resistance leader Captain America on the court house steps after his capture.

A deadly brawl at a reality TV show between super humans caused new laws to be passed requiring Super Hero registration and turning over their secret identities to the government as individual weapons of mass destruction. Some government affiliated super heroes, and others, supported this law while some fled to other countries and some started an underground resistance movement. Captain America became the leader of the resistance but had just turned himself in over dangers to civilians in the ongoing battles when he was assassinated by what may be agents working for super villain Red Skull.

Captain America had been presumed dead before. At the end of WW2 his plane blew up but many years later his body was discovered frozen but preserved by the super soldier serum that gave him his powers. Technically, Captain America always claimed to have just the body of a human developed at its maximum potential. More recent science suggests genetic modifications by the serum and virus and the unknown rays in the treatment. In the 1940's it was probably not nanobots.

The long glorious and patriotic history of Captain America wiki.

As with the death of Superman in 1993, and even previous incarnations of Captain America, someone usually will step into his costume and continue the saga.