Ok, some of u may not understand, but i believe some will.
He's fat and he farts...
Boomer is a rare - one of a kind animal which likes to fart and vomit all the time (mostly fart), and time to time explode, making some weird farty sounds, like *Frrrrrt*
As people used to say, where there are boomers, there will be molotovs and in extreme cases, pipebombs for the little fartlings (children of boomer), which he releases upon people when he tries to stink up the place.
Notice the big hairy zits on his body (I claim this planet in the name of Ed!) , and the fat and toxic substance he calls a body.
Sometimes his farts doesn't kill u instantly, but you will never be the same if you experience it.
"*Frrrt* Hmm?" - thats the most common phrase boomer makes, nontheless, he can't make out anything else, sometimes maybe just *frrrt*.
Rumors has it, that he also owns a dog, which is called McFart the crimehound, unlike the dogs from Zombies 1.41, his dog stinks just as much as boomer himself.
Boomer is still waiting, as his "Want to make a prank on your friend? Fart coushins are the thing of the past. Try out new - Boomer Farts in the can. That will blow your friends head for good and he will remember it for the rest of his life!" is Pat. Pending.
He goes to the gym once a year, when he tries the trampoline, it dissolves once boomer is in the air, and people in 5 mile radius hear a terrible sound, which is something like this "Kablam *Frrrt*" Afterwards, men in swimsuits are are called to scout upon the scene of disaster.
And my most favorite phrase about all this boomer madness! (which i made up myself, and only true fans of l4d understands it)
Q: What phrase makes a boomer run far far away?
A: "Molotovs?! Hell yeah!!"
And for fast movement, he uses Quad-Ass propulsion system