Honey bees are not aggressive, and do not search for something to attack. Instead, they are defensive and will attack only whatever seems to threaten the colony.
Swarms first move to a temporary site such as a tree branch. The swarm will usually remain here for about 24-48 hours until permanent quarters are located, and then moves on. Permanent quarters may consist of a bee hive, hollow tree, hollow wall, attic, etc., typically some place which is sheltered from the weather.
Bees in a swarm are very docile and not likely to sting because they harbor no food stores or young and therefore, have nothing to defend. Likewise, honey bees encountered away from the hive are unlikely to sting unless severely provoked, like stepping on them. However, if the hive entrances approached, the guard bees can become very aggressive. Worker bees have barbed stingers and when used, the stinger, poison sac, and associated tissue are torn from the body. If the stinger is not removed immediately, muscle contractions will drive the stinger deeper and deeper into the skin and there is a greater time for toxin injection. In addition, the stinger gives off a pheromone which attracts other bees and induces an alarm and attack behavior. Therefore, immediate removal with a fingernail or knife blade is recommended; squeezing only forces more venom in.
Africanized honey bees are much more aggressive and will sting with little provocation, even swarms may be dangerous. They will persue the intruder/victim for up to 328 feet whereas, domestic bees pursue only about 33 feet. They use a wider range of nesting sites, sometimes including subterranean cavities.