Yes, they could absolutely kill you. The Cassowary is a solitary animal that prefers avoiding confrontations, especially with humans. However, it is very brave and will stand its ground if approached.
If an intruder encroaches on its space, the bird will stretch itself as tall as possible, ruffle its feathers and let out a loud hiss in an attempt to scare the intruder off. If this fails the cassowary will lower its head and produce a deep booming sound as the pigmentation of its skin on its neck becomes much brighter and its body trembles. It will then attack fearlessly.
The Cassowary has very powerful legs with dagger-like claws that look like spikes that grow up to 18cm in length. It attacks by jumping up in the air and kicking forward with its legs. Its lighting fast kick, with dagger sharp claws, is powerful enough to severely injure or even kill its victim. Once provoked it will keep up its attack chasing its victims at speeds up to 50kph.
Cassowaries have a reputation for being dangerous to people and domestic animals. Statistic show that this reputation is ill-founded. The last recorded death of a human due to a cassowary attack was in 1926. This too was in self-defence when a teenager attempted to attack a cassowary with a club.