How do I cope after witnessing a medical emergency during chemo?

Today i had 4th chemo treatment. 1st time at this office. I have stage 3 b cell lymphoma. I feel good considering it was crowded. I had a companion drive me and stayed. All was good until halfway thru. Another patient began coughing all staff ran to him..as we sat by watching. He left on a stretcher. This disease dont play. Office did everything right but our bodies reject the drugs and develop allergy mid treatment. Prayers he is ok. He was alone. He came around same time as I did he seemed very healthy. Strong.we know.you can't tell by looks. Im not going to lie. Im shook. Im resting. But hard to refocus. Can't say im not scared. The 1st three treatment were in hospital. I was there 3months after flat-lining i had a trac .and part of mass removed to fit tub. Can not eat as it is in throat pressing thyroid and vocal cords. Thank you everyone for letting me vent.