2004 Dodge Stratus 2.4L

2004 Dodge Stratus 2.4L engine just died while driving. Mechanic says no compression in 3 of the 4 cylinders. The timing belt looks good and is tight. Mechanic says there is another belt below the timing belt that might be bad. But he says he thinks it probably bent the valves. I have no idea about another belt. But I was thinking maybe it just jumped the timing and threw everything off. From what I can find, it seems like this is a non-interference engine.