Filter Spitting Sand into the Pool

I'm new this season to both pools and the Pool Forum.

We recently purchased a home that has a 24', AG pool with a Hayward 1 hp pump and sand filter.

Finally got through setup (thanks to the Pool Forum) and have been swimming for weeks now, without issue.

Suddenly noticing sand in pool after running filter. Turned it on yesterday and saw the clouds billowing into the pool.

I have NO idea the last time the sand was changed or how old any of it is (neighbor thinks everything is about 6 years old).

I have no idea if or how to open any of it up to investigate (can you after pool is in operation?)

Help.

Sounds like it may be a broken lateral or something. Poconos or somebody will be along shortly to offer some help. But, one thing I can tell you is that it is NOT because you need to replace your sand. Nor add "sand cleaner." These are both things that pool stores may try and tell you. I have had the same sand for 10 years, CarlD has had his for 8 years I think and Al (Poconos) I think even longer than that.

Had you backwashed your sand filter just before that happened? Backwashing can cause sand to blow back into the pool when you subsequently turn the pump on if you forgot to put it through a rinse cycle.