Have had no problems with the car till today. I was stopped at a light,

What is your question?

Started to drive and the car just shut off. Did not stutter just stopped. Had enough movement to get it to the curb. Tried to start it sounded like it wanted to start but wouldn't turnover . Gas was below 1/4 of tank my mechanic said to add gas gauge could be off and I may have run out of gas. Added gas but still wouldn't turn over. Called AAA when tow truck came and tried to start it. Nothing happened said battery could be old and from trying to start it I could hVe drained the battery . It at the mechanics now but being it's Sat. He won't get to ck it till Monday. Any ideas what the problem could be?