Trevis Austin, a black cop, wasn't even indicted for shooting/killing unarmed Gilbert Collar, a white teen. Officer Mark Tiller, white male, shot and killed white teen, Zachary Hammond, while he was trying to escape (re: leaving, not attacking) over suspicion of marijuana possession... Tiller faced no charges for the murder. Gilbert Flores, a white man, was shot and killed by officers despite video showing his hands up in the air. Iowa man, Ryan Keith Bolinger, also white, was shot and killed by police... the reason for chase is that he was dancing in the street (hardened criminal, obviously), and it was believed he was drunk or mentally ill, and known to be unarmed, at the time he was shot and killed. Dillon Taylor, a white man from Salt Lake City, was also unarmed and shot and killed by police... no charges were filed against the officer who shot him. Etc...
So yes, all lives do matter. Police shooting and killing unarmed citizens is not a race issue. Statistically, more white people (compared with black people) are shot and killed by police. Albeit the US has a higher white population than black population, so logically it's possible (and even likely) that - per population - there's a higher percentage of incidents involving police shooting/killing (often unarmed) black people; yet per number, police are more likely to shoot and kill (often unarmed) white people... including several cases of black officers killing white citizens.
It's also worth noting that despite the incidence of officers killing unarmed citizens is WAY too high, it's actually not a common thing. There are also over 600,000 calls to the police every day, and that doesn't account for surely hundreds of thousands more traffic/warrant/crime in progress stops that officers witness and respond to. 2015 had an abnormally high number of fatalities - officers shooting and killing citizens - at *almost* 1,000. It's difficult to find a statistic on exactly how many police responses there are per year (factoring in traffic stops, warrant/seeing someone matching the description of a suspect, witnessing a crime in progress, etc...), but a common number appears to be 240 million calls to 911. So, the number of responses would actually be higher, but the number of deaths the same. Doing the math (1,000 being x percent of 240 million), that means 0.00042% of police responses result in a citizen's death... which is incredibly low (and it would be even lower if accounting for responses beyond 911 calls).
So, while officers killing citizens is definitely a problem that needs to be addressed, it is not actually an especially common problem (despite what media promotion of a few select cases would have one believe). And, with white people being the majority of those killed by police, it's also not particularly a race issue.
So, yes... black lives matter, but all other lives matter, too. Focusing solely on black victims does not even begin to address the issue of police violence/brutality/murder, and only serves to alienate the majority of those affected by police violence (the majority being white people) and leave their voice out of the issue of police violence, despite being the most likely to be killed/the most likely to be affected by a loved one being killed by police. Yet again... police shooting/killing citizens is not especially common, despite what the media would have you believe.
Choosing to ignore that reality - choosing to ignore the reality of white victims being the majority of victims of police violence - is willfully ignorant, and an ignorance focused solely on your racial bias. It's also worth noting, in the case you mentoned, that the officer was convicted of manslaughter (then reduce to criminally negligent homicide), not murder. Manslaughter is a lesser charge than murder, and criminally negligent homicide is a lesser charge than manslaughter. But it's apt, based on the evidence - Liang did not intent to shoot Gurley, or even know that Gurley was there, but made a poor decision when pursuing the actual suspect and that resulted in Gurley's death. Whether you think that should be charged as more or not (personally, I think the charge should've stayed with manslaughter and not been reduced) - that's up to you. But unlike so many other cases (including cases of black cops shooting/killing white citizens), Liang was actually charged with *something*... many are not.