Looks like someone either figured the capacity of the slings wrong, failed to properly inspect the slings before use or didn't use softners where needed.
Notice the worker to the right in the foreground. The loco is on the ground before he can do much more than flinch. I've worked with people who are sometimes careless about getting under a load. When you call them on it, they'll often say that they were ready to run. I tell them that they were ready to die! Not to mention that if seen by management they will be fired on the spot!