From a legal standpoint, it actually depends only on the laws or the place, where such action would be committed.

From a moral standpoint, it is also unclear.

What is certainly not right, is to attack anyone with an intention to kill, if there is any other realistic way to protect your and your family members' lives. It is not right to kill a human over any property, but it may be OK to kill the offender to prevent a murder. It is unclear from the Telegraph's article (which is common for that source, since Telegraph is the tabloid), if there was a clear life threat or not, so the police has to take action and investigate that matter.