Shattered Timing Chain 2000 Altima

[chocolatemessx10]

Please help
I bought a 2000 Altima GXE in Aug 2006 with 44k miles on it. The car wouldn't start and I took it to a mechanic. He showed me the timing chain (or what was left of it). It had shattered, there were parts of the chain all over the engine. When he removed the guides, the plastic guide was broken and the metal one had gauges in it from where the chain had worn it down. The car now has 75k miles on it. The mechanic also said that he saw "bearing shavings in the oil pan". As he showed me the parts, he said that the chain should last the life of the motor. He told me that the car has more miles on it than it is showing. Has anyone heard of a timing chain on an Altima shattering at less than 80k miles? I am basically lost as to what to do.