Why was mandisa relieved to see the police but then suddenlt apprehensive about their visit

In this short chapter, Mandisa's home is raided by the police in the middle of the night. It is 4 AM, and Mandisa doesn't know what has awakened her. "We said open up an hour ago!" they yell, "What'ah you trying to hide?" (62). Although they are wrecking the home, Mandisa is relieved to see that they are, at least, actually policemen. Soon after relief comes worry—what does it mean that they are there? The police are not exactly comforting presences in the community: "The police are no security to us in Guguletu... I remember people killed by the police... including children" (62). Mandisa has lost sight of her husband in the commotion.