transmission question

My brother in-laws musting is having a problem:

Its stuck in first gear and moves freely from first/nutral/second without the clutch being applied. This happend when he was driving and shifted into second, there was nothing there. He tried to put it into third and it worked but after we stopped he put it in first and it never came out again.

('96 Mustang GT T5 shifter)

Any suggestions??

linkage could be bad, dosent sound like it
clutch?
But with stuck gear, sounds like a syncro...I had that prob with my 67 mustang, stuck in highest gear (3rd).

Check your fluid, if its low, post it, because then it could just be a stuck gear.

I total agree with T-Velocity.

I would be leaning towards the syncos, but thats a total guess.