HI
I have had two patients after ACL reconstruction who have suffered from hamstring tears. This is not surprising if part of the hamstring has been harvested to make the ACL graft. Means the remaining fibres are under more stress. Also to consider: Hamstrings are having the same function as the ACL: to stop the tibia sliding forwards under the femor (anterior drawer test). So ACL injuries will have increased hamstring tension anyhow because they are trying to compensate.
The hamstring also has the function to decelerate the swing of the tibia into extension:meaning it has to activate whilst being lengthened. This will proof a difficulty if a) it is to short/ thight and b) if it is to week.
Very telling is the snap you heard, the localized tenderness over the hamstring. If you still need more proof: it will be sore if brought on length (single leg raise with extended knee), it will be sore if activated against resistance (lying on your front, bring heel to bum). Likely there will be bruising in a few days time.
Of course initially after injury and depending on where you are in your rehab this might not even be possible. I would youse RICE (rest, ice, compression, ice) for 24-48 hours, NSAID if not contraindicated and then start very gradually with some bending and straightening without resistance (in lying, then in front lying) and some very gentle stretching for the hamstrings.
About wether you have damaged your ACL : most likely not, but let it be tested with the anterior drawer test. Also your knee would be quite unstable.
I defenetly would get a physio to help recovery along: making sure to treat the hamstring injury first. THis incident will set back your recovery time a little but hopefully not more than 2-3 weeks depending on the extend.
Just as a word of causion. Done over the net, without seeing you, all the above are assumptions from my part and have to be varified by a trained physio or consultant.
best of luck!