Out of curiosity what was the breed of dog that killed your in-law's dog?
We had 3 neighbor's that had a breed, (can't remember... wanna say Akita but I could be wrong), that killed neighboring dogs often. This was over a long span of years. One was a break-in thru a backyard fence.... (like your situation)... the other two were people out walking their dogs when they were attacked. No people were harmed, and they tried to fight them off but they killer dogs couldn't be stopped... predatory instincts made them ferocious. - JamesJM