My fish died after I did this to it?

The bait minnow could have been diseased. Bait fish are only meant to use as bait not as a pet. So it probably had some sort of fish sickness that you didnt know about. Sorry to hear about your loss. You really shouldnt have done that though. It is just like how people use dogs for dog fights. It is very wrong and cruel. i am sure you learned your lesson, hopefully it wont happen again.

Unfortunately, yes, it could have died because of the minnow. But it probably died because of the bowl. Betta fish can also be kept with some other fish, like white cloud mountain minnows. Rosy red minnows from feeder tanks are often infested with diseases. But I am 90% sure the bowl killed your betta. Did you check the water for Ph, Nitrates, Nitrates2, and ammonia yet?

The betta might have died from the stress of the minnow and him feeling territorial just incase the stranger came back.

No it probobly wasnt because i have a betta and three minnows in my 10 gallon and my betta is fine even though i have seen my betta atacking them

Hopefully that minnow didn't infect both your fish and dog.

The minnow probably had a disease and gave it to your Betta. That was a stupid thing to do!