19.5 Briggs & Stratton dies while mowing

Sounds like a engine tuning problem.
Mixture too rich under load .
If you have a briggs and stratton engine you can probably find help at this site.
Manuals Parts

tuning four cycle lawnmower engine YouTube

Did it leak oil & seize up

Can you turn it over by hand

Is a belt or bearing preventing the motor
from turning?

check for spark when the engine dies you might have a bad coil

did you hit something while mowing the key way between the flywheel and crank shaft might have sheared it will act like the blade is missing pull back on you while pulling the rope

Use Briggs & Stratton ethanol free gas it is already mix and ready to use or any ethanol free gas that's ready to use.

sounds like throttle cable come off

first make sure the air intake screen on top of engine is not clogged with debris if thats not a concern you could have a faulty ignition coil etc your engine should have a two year warranty and can be serviced at no charge to you at your local briggs service dealer make sure and check your manual for the fine print though. Briggs makes a great engine and very rarely have I ever seen a problem allthough if you were to have an engine issue it will accur during the first few hours of opperation good luck

If it starts lightly smoking black smoke at high RPM it is flooding or getting too much fuel. The float is leaking you may have not set the float height correctly when you put that carb back together. Or the needle and set could be bad.

Go to sears parts direct.donnyb60