What...
. The value of human life gets cheaper by the day. Killing someone for stealing is not acceptable.
...is appropriate then?
A person(s) decide, of their own free will to cross a line, to take another persons property. That is at the very minimum immoral and I would argue it is evil. When you take someone else's property you have taken their property, you have taken their efforts that went into acquiring the property be it work, a gift, you have taken the planning on getting the property, you have taken their time and effort going and getting it or building it or what have you.
Then there is the attachment to the property, enjoyment of it, the satisfaction of acquiring it, any and all friends, family and neighbors who also derived something from it be it giving or helping or what have you.
Further, a persons right to privacy has been violated. Their peace, their sanctuary has been taken. They have been violated far more deeply than losing something that belongs to them.
A thief has subjugated another human being both temporarily for the actual crime and permanently for the lasting emotional impacts. He has attacked them both physically and emotionally. Do you even consider stealing wrong? If so, why? Do you dismiss out of hand each and every violation that is inflicted on a person when they've been robbed? What is fair to 'give' all that back? What is just?
This man saw wrongs being committed and he reacted correctly, rightly and justly in taking action as a citizen to say "NO!! I will not stand by as you do these crimes!". He is a good citizen, far better then these criminals. He is not the one who brought injustice and crimes. He is the one who stood against them.
They chose of their own free will to inflict upon others, innocent others. What's to prevent them from choosing to cross more lines? Maybe the dog barks a them? Maybe they choose to kill it? Or poison it? Maybe someone is home, asleep? A child? A grandparent? A witness! Now what? Who will know? Maybe they tie them up? Murder them? Rape them? Why is their judgement as to how far they would go to be given some sort of pass? Who is to know, at the time, that they 'only' wish to 'simply' steal? Now they've entered into terrorizing another, innocent human being(s).
When you've done wrong, you've brought this upon yourself, the right of others to oppose you..
When you've done right and tried to prevent a wrong, to punish
that person, now THAT is evil.
A person has no, NO right to inflict upon another person, an innocent person.
These two getting killed committing these crimes is nowhere near what they were doing to others. You want to talk about value of life, you start with what has been inflicted upon innocent people and what is appropriate sanction to not only punish offenders but to discourage others.
The value is not the criminal. He acted of free will to inflict. The value is in what the criminal has taken.