USA vs EU
In the USA, the complainant gets to "press charges", after which the police acts. If the complainant is somehow pressured into withdrawing that complaint, or if the complainant disappears, then the authorities is very restricted in its ability to pursue the complaint. It's a primitive system that encourages certain parties to make sure the complainants do, in fact, disappear.
In the EU and other more civilized countries, the complainant goes to the authorities and makes a complaint. The authorities then carry the ball from there. The disappearance of the complainant can be quite immaterial to the subsequent prosecution of that complaint. All in all, this type of system reduces the risk to the complainant, and also allows justice to be done if the complainant is "neutralized", as has happened this time with PSI.
Personally, I like the second system better.