Whilst playing the game he could have died in many ways like getting killed by infected, falling of an edge or friendly fire... You can find him locked in cupboards through a level and bring him back. He will also be alive once you have finished a chapter and go onto the next one.
Chat with our AI personalities
you have to die at the end
the campaigns for left 4 dead are: NO MERCY BLOOD HARVEST DEAD AIR DEATH TOLL
There are a few sites, check out the Left 4 Dead forums online.
4 players can play in Left 4 Dead 2.
There may be a Left 4 Dead 3. I think they started making it September 2011.