The argument that guns are inanimate objects and therefore do not kill people does not apply in all situations. There are countless of inanimate objects that are responsible for death. There are plenty of things that are not living than have the capacity to kill.
For instance, the environment is an easy example to use. Harsh weather conditions such as hurricanes, tornadoes, and earthquakes can kill people. Air pollution and natural fires can be many’s people's demises. For instance, Hurricane Sandy of 2012 was the direct cause of 147 deaths.
Such an event has no moral compass nor mental state, but it had the capacity to kill nonetheless.
Inanimate objects, things, and events without moral compasses nor freewill can murder and kill people too. Guns can kill people, and they do.