Do Christians that commit heinous crimes still go to heaven?

Please remove if not appropriate. I really mean no disrespect and just want to understand your guys perspective.

My devout Christian friend was saying something along the lines that as long as you believe and accept Jesus Christ as your lord and savior, you will receive salvation no matter what. Salvation cannot be taken away.

I then said what happens if a Christian who has believed and accepted commits an absolutely heinous act like murder. Is that person still saved and will be with God when he does?

My friend said yes.

I even further said okay what happens if the person he murders is not a believer of Christ?

He said he would go to hell because he had the chance to know God and believe but didn’t.

So I’m just confused and I feel like it’s unfair isn’t it? I feel like I’m operating on the assumption that God is fair and just which I’ve heard many times before.

What are we missing here? What are your guys thoughts?

Thank you!