weird problem please help :(

the car is a 96' eldorado ETC. driving home from school for winter break with my cruise set at 74mph all of a sudden the engine turned off and i was able to drift into the median. No noises, no smoke, no change in temp., no oil leaking. the car would fail to restart and only crank and crank and crank. After getting it home 2 days later we charged the battery and cranked it again this time there was a loud gun shot noise and smoke came out of the passenger side of the engine. after up on th elift no sign of any leaks or other problems. I recently had the fuel rail replaced but have driven 1,500 miles since. the antifreeze is at a normal level and this symptom of the loud gun shot noise only does it after its been sitting and it still does not start just cranks and then BOOM and smoke. there are no messages on the dash. we checked the fuel pump and that appears to be working fine. any help would be greatly appreciated.

Thanks again,
RJO

we just took it in and it appears to be timeing belt sorry to say it but i think my baby is going to the curb