Around 7:00 a.m., Racak was surrounded by the Serbian police. Several witnesses told Human Rights Watch that they saw seven blue armored vehicles on Cesta hill, as well as three VJ tanks (type T-55). The police were shooting and some heavy artillery was fired directly into some houses near Malopoljce and Petrovo from a position in the nearby forest called, in Albanian, Pishat. The extent of the fighting in Racak that morning remains somewhat unclear. According to one Serbian policeman, the KLA's resistance around Racak lasted almost four hours, and when they were finally able to enter the village the police confiscated three mounted machine guns. Villagers, however, said that the police had entered the village by 9:00 a.m. They said that there was shooting and some artillery until 4:00 p.m. By 4:30 p.m., the police had left the village.
Also, the description of the AP team's videotape implies that the reporters accompanied the MUP's vanguard, although there's nothing explicit to this effect.
The Serbs sought to investigate on their own but were prevented by the KLA. From The Times (#15):
The regional prosecuting magistrate, Danica Marinkovic, was said to have again entered the village, although she refused to talk to journalists. Late on Monday she was reported to have had the back windows of her Lada Niva shot out by a Kosovo Liberation Army sniper as the police removed the Albanian bodies from Racak mosque.
And from Reuters (#7):
Danica Marinkovic, the judge investigating the killings, said on Sunday she had been unable to reach the site. ``For the third time I tried to make an inquiry but I was stopped by the terrorists,'' she said, referring to the KLA guerrillas.
As you know, the investigation was "internationalized" soon after.
As for your comment, we both know killing an Albanian wasn't considered a crime in Kosovo, I'd have to say no more nor less than, for example, killing an Arab in Jenin or a Somali in Mogadishu. And far more so than, say, killing a Serb on Varvaran bridge or in a train outside Grdnicka.
As to any Serb investigation, how many MUP members have given statements, to whom did they give them to, and what has happened to those statements since? I remind you that the Serbs retook Racak after the 15th in order to retrieve the bodies, so they appear to have been willing to do one thing (gain control over the forensic evidence in the form of the dead) but not the other (secure the crime scene to allow investigators to do their work).