Miscarriage a week after hearing heartbeat

Went in for an US on 2/21 and was measuring 2 weeks behind I calculated I should've been 8 weeks 3 days but had a heartbeat if 145 which she said was a good strong HB. Had some brown discharge when wiping but didn't think much since I heard HB on US. Started bleeding when wiping the other day called the doctor this morning and they sent me in for an US. She did a transvaginal US and told me there was no fetal heartbeat 😢 I just am in complete shock after seeing baby a week ago with strong heartbeat. I just feel like if I would've called a few days ago maybe they could've done something. Just so sad my 3 year old was so excited to be a Big Sister! Hopefully God will still make that happen for her and for us!