When people overestimate the frequency of violent crimes because these events generate a great deal of media coverage, they are using?

I believe the answer is: Availability heuristic

Availability heuristic is an occurrence when people choose to rely on simplistic examples to discuss a certain topic rather than choose to analyze it with a more complex method. In news, this would make people attribute social problem to specific group of people or a specific party rather than giving it a full thought.