I'm not sure exactly what your question is.
If, you give a shot, hit a blood vessel AND NOT ASPIRATE what happens?
Or, if you give a shot and it squirts blood halfway across the room when you withdraw the syringe?
Over the past seven years or so I squirted a lot of blood. Never have I landed squarely in a vein at the tip of the needle to suck in blood. Nicked some on the way in, or more, but never in the muscle. Bad veins run my family, I had a few stripped already.
When you squirt, most likely it was a skin or fat capillary or vein you hit on the way in. Deeper ones (Which I've hit) will make a big bruise and swell more since the blood is trapped better in the deeper muscle & fat layers plus the fascia holding it all in place