Sin of Omission-Venial or Mortal?

How does one determine whether a sin of omission is mortal or venial?
For example, if I see an injured person who is at risk of dying due to their injuries and I do not dial 911 or provide first aid (depending on my capabilities and knowledge), that would be a mortal sin of omission.

But what if I see a dangerous object and do not warn others about it, resulting in an injury should they come in close contact with it or I notice that a person’s shoelaces are untied and I do not notify them, would these be considered mortal sins? My problem is that I tend to keep my mouth shut and think “it’s not my job to do that” or sometimes I am indifferent towards others.

I don’t know, but I personally believe that omission is just as bad as commission. Worse actually, because it tacks on dishonesty as well.

If you shoot a man in the shin and leave him to bleed to death, then you are a murder. But if you see a man bleeding and you walk past him without trying to help him, then you are a murderer and a liar as well for pretending that it isn’t your problem.

If you are a human being, then you have a duty to help other humans.

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