Brake Hoses, Lines/piping, And Fittings problems of the 2000 Mercedes Benz M Class

Without any warning, when coming to a traffic stop the brake pedal on my 2000 mercedes ml55 went to the floor. I was able to stop after reapplying the brake and pushing very hard. Fortunately no cars were in front of me or I would have hit them. I pulled to the side of the street and looked under the hood, noticed the brake fluid was low, put some fluid in and drove a short distance to work. The brakes were very soft. The next day took the vehicle to my mercedes dealer where they found that a brake line was rubbed through and leaking. No indicator lights or warnings of any kind occurred before the problem.