It is unnecessary to see the ASSAILANT, not "victim", commit any felony. All that is required is a reasonable suspicion of a crime.
Wrong - the relevant law
clearly states:
"A private person may arrest an offender if the offense is committed in his presence or within his immediate knowledge. If the offense is a felony and the offender is escaping or attempting to escape, a private person may arrest him upon reasonable and probable grounds of suspicion."
The killers witnessed no crime. If they had "suspicions" that the man they killed had committed a crime, that crime would have had to be a felony. What felony did they suspect the victim of committing? By all indications, they thought he was pilfering things from a construction site - a misdemeanor.
If they hadn't shot the victim, they'd have been guilty of false arrest. As it is, they're guilty of murder.
Stop trying to move the goalposts and stop believing everyone is dumb enough to accept your changes to what the law actually is.
Read the law and try to get it through your head that the two idiots you're white-knighting for are murderers.
The killers witnessed no crime. The citizens witnessed the crime of trespass, and had reason to believe the recurring trespasser whom they had seen on several videos spanning several months, was the thief.
Yes, they had probable cause.