Do Tetra eat eachother? what happened to my poor fishie?

I have too small tetra and 3 larger ones... well not anymore D: I woke up this morning to find one of the big ones gone!! It did not look sickly, or a loner or anything and was never picked on by any of the fish. Our tank is covered and its impossible to jump out of. I am feeding them the right amount and if they were over fed, then wudnt all them die? The tempature was also fine, although we have only had our tank for about 3 weeks. Please explain to me where my poor little went!!