Sorry to hear - sickening when that happens!
Belts can snap for loads of reasons, even when fairly low mileage on them. (incorrect install, failed tensioner or idler pulley, failed waterpump impeller locking shaft, slight burr or nick on one of the toothed pulley's damaging belt, or nick on belt itself from new or during install, etc, etc).
More often than not valves would be bent on the EJ engines, but not always.
Had a belt snap on an Impreza v3 STI about 10 years ago, and my money was on bent valves (and that is what most people here on the forum thought too). However, I put a new belt kit on it (which would have been needed if overhauling whole engine, or putting in replacement engine anyway - so shot to nothing really)... turned it over by hand and all sounded ok... next did a compression test and full healthy compression on all cylinders, so started her and all was good! Did another 12k miles with her before selling and never missed a beat, no untoward noises, no oil usage... just all good.
So, if it was me I'd be doing the same thing in your case as either way a new TB kit will be needed. Fit it, try compression test. If all good then count yourself real lucky (like I did), or if engine no compression then remove engine and either fix or find a replacement that is suitable and fit that new TB kit on that.
Good luck and fingers crossed...