Replying to Car won't start

hey what's up people knowledgeable about cars...

my friend has a pretty old car, and he left it parked this week since sunday, and then went to start it yesterday and it wouldn't. lights went on and stuff, and it'd try to turn over but wouldn't. he checked the oil and it was bone dry..

obviously we're going to get it diagnosed by a mechanic but for the meantime, can anyone tell me how likely it is that the problem is the lack of oil? there were NO warning signs or weird noises before hand....just parked it and left it for a few days, and now it won't start

thanks