Cannot pull starter cord on chainsaw shut down while running

SOURCE: Chainsaw won't start

Time to get out your trusty tool kit. Remove the side cover assembly and look at the recoil assembly. You should see a pair of fingers that when you pull the cord move toward the center. If the fingers are there and not broken, make sure they move when you pull the cord. clean them if dirty or have foreign objects (like sawdust) around them. If the fingers are broken, replace them. You should be able to purchase them from your local saw shop.

SOURCE: My echo 400 chainsaw was

This does not sound good, start by removing the starter, try to turn the engine by hand turning the flywheel, move it back and forth incase there is somthing trapped between the flywheel, if you cannot turn the engine this way, then somthing bad has happened inside the engine, it will now require a strip down to find out exactley what has happened