Atleast tell them

Ezekiel 3:18 When I say unto the wicked, Thou shalt surely die; and thou givest him not warning, nor speakest to warn the wicked from his wicked way, to save his life; the same wicked [man] shall die in his iniquity; but his blood will I require at thine hand.

Most believers have a funny mentality towards soul winning. They think their actions are enough to get the onlookers saved. They forget the important aspect of speaking forth the Word.

There's a place of accountability we have to give before God for having not told the people to turn away from sin, the devil and even themselves to God. 

Atleast inform, warn, them about the consequences of their not choosing Jesus and God won't hold you accountable for their eternal death. Sin is not only doing what's not right, its also knowing what to do and not doing it. Sin is both in the things you commit or omit. 

Let's do the great commission and avoid doing the great omission. 

Further scriptures 

James 4:17 Therefore to him that knoweth to do good, and doeth [it] not, to him it is sin.