My current project is a high school drama/sci-fi action story revolving around a group of people fighting an alien infiltration. In this story there are multiple races who use a variety of weapons, for instance the Dur (gaint mechanical grasshoppers) use weaponised nano-machines to tear their enemies organs apart from the inside out, the Guratla (reptilian humanoids) use short range heat guns to melt their targets, etc etc. Anyway, the weapons I'm struggling with are laser pulse rifles, they work by firing a highly concentrated beam of light... but that's all I know. My question is what kind of effect would this have on a target? How exactly would it work and how effective would it be in an urban environment (lots of cover, lots of smoke and particles to get in the way of the beam)?