The primer explodes, releasing heat.
The heat ignites the gunpowder, a mixture of carbon, sulfur, and saltpeter.
The shockwave from the tiny explosion propels the bullet. In an instant it leaves the barrel of the Uzi submachingun, flying through the air at near the speed of sound.
The air does little to hinder this bullet, an alloy of lead and antimony, as if carries the energy of the gunpowder explosion.
It then comes into contact with something solid, plant fibers woven into a sheet. For an insdtant it presses against this and what is behind this.
Then it tears through the cotton fabric.
Then another layer of cotton fabric.
Then through skin, muscle, lung tissue, blood vessels.
Before coming out the back, considerably slowed.
And finally striking a brick, flattening itsa shape.
The bullet can not know the reason for its journey.
It has no idea of a Vietnamese gang staging a hostile takeover from the long-established Chinese triads in a place called San Francisco.
The bullet isd simply fired from the cartridge, and that is that.