Dallas was rocked by the deaths of many police officers who were guarding a peaceful protest in the city. Now, another set of police officers have been killed. This indicates that more people are believing in an "us vs. them" sort of mentality that leads them to mistrust (and, in extreme cases, kill) members of the police force.
Violence against police officers is on the rise. Although it is easy to dismiss the recent wave, there has been a study that confirms the increase. There are a lot of reasons, including increased mistrust of the police and easier access to guns. The recent media coverage only increases the motivation for those with negative feelings towards the police.
I don't know specific statistics on this topic, but based on news coverage it suggests that violence is on the increase against police officers. It also depends on whether this question is country specific or not. In America violence against officers has been on the increase recently, as a result of the treatment some white officers have given to black people. As things stand there is no reason to believe the levels of violence will recede until action is taken to please everyone.
Either violence is increasing or the media is finally reporting on it more fully. Both ideas are true and both are really awful facts. For a long time, many Americans felt the media only reported on a certain 'kind' of violence, now that everyone is getting in on the 'rage game,' media must report on all forms of violence. And all forms of violence are increasing. Want proof besides glaring and disturbing news outlet blerbs? Just take a look at the statistics behind our incarcerated citizens, those in particular serving time for violent crime.