Through a variety of mechanisms
-----------------------

**Blasters pierce, burn, and cauterize. They also have a decent amount of kinetic force.** 

From *Aftermath*: 
> A bright light. The bark of a blaster. 

>He cries out in pain as a laser
> bolt burns a hole through his shoulder. His hand reflexively opens—the
> microphone clatters away. He paws at his hip for his own blaster, but
> another shot and the weapon that hung there is quickly spun to slag
> and knocked off his belt.

><sub>*Star Wars: Aftermath*</sub>


Despite continuing the tradition of poetically (and inaccurately) referring to blasters as “laser bolts” even after that aspect had been dropped, this makes it clear that blasters can indeed burn through people. 

Even more explicitly:


> Cobb Vance’s hand is up in a flash—there’s the shriek from his own
> blaster, and it punches a cauterized hole clean through Adwin’s
> shoulder on his right side. His hand goes limp, lifeless. The helmet
> clatters out of his other hand. He backs against the shelf,
> terror-struck.

><sub>*Star Wars: Aftermath*</sub>

Lest we imagine that this is merely the description of one novel:


> “Tai-Lin.” She rolled him onto his back in order to assess the wound.
> “Tai-Lin, can you hear me?”
> 
> But of course he couldn’t. He had been hit directly in the chest, at
> close range, by a blaster set to kill. The deep wound where his heart
> used to be had been cauterized, leaving a blackened crater behind.
> Arliz Hadrassian had avenged her Amaxine warriors.

><sub>*Star Wars: Bloodline*</sub>

This also indicates that at closer range, blaster shots can cause rather explosive damage. Indeed, they seem to have enough kinetic force to blast a droid’s face off: 

> Norra’s on the ground—her back against the metal, her blaster up and
> firing at a droid diving toward her. Her shot tears the thing’s
> faceless mask off, exposing a sizzling circuit board. It collapses
> against her, limbs flailing uselessly against the metal—she rolls it
> off her and fires two more shots into its open skull. It stops moving.

><sub>*Star Wars: Aftermath: Life Debt*</sub>

As the new canon novels indicate, blasters are not clean weapons, nor anything like purely concussive. They are probabably not *bloody*, for much the same reasons as lightsabers (their intense heat), but nor will they leave only minor burns.