It looks like officer Sicknick didn't die from being hit on the head by a fire extinguisher.
“Authorities believe Sicknick's death was driven by a medical condition,” ABC News reported, citing “sources familiar with the matter.”
That's an old link! They found or got video of the incident, identified as an ex fireman. and arrested the guy who threw the fire extinguisher.....which hit 3 policemen in the head, bouncing off their heads on to the other....two with helmets, one without.
The policeman that died, developed a blood clot in his head from the injury, and had a stroke from it.