The first thing yo need to do is check for spark while cranking. More often than not, when one just dies suddenly it's ignition related. Did it sputter for a while before dying, or just shut off?

'91 LWB, 31x10.5s, KYBs, A/T "I look like Robert De Niro, I drive a Mitsubishi Pajero" - Billy Bragg (not the original lyrics, but that's how he sang it when I saw him in Dublin in '04)