LACI PETERSON'S FINAL MINUTES

Pregnant Laci Peterson was punched in the stomach and beaten to death by her cheating husband Scott!

That's the chilling scenario sources close to the investigation laid out after Scott's April 18 arrest on charges he murdered his wife and unborn child.

The issue that goes on sale Friday reveals how cops believe Scott killed Laci -- and why -- the secret evidence against him, how cops used Scott's lover to trap him … and much more.