He may well have had a stroke, since his family said he had a blood clot on the brain. While the specific cause of death has not been officially released, no one has suggested that it was unrelated to his injuries. Even if he experienced a heart attack subsequent to being injured, it would be the trauma from the injuries that resulted in the heart attack. Any way you cut this, his death was related to his violent interaction with protesters in defense of the Capitol building and the people within it. Because of Covid-19, there will not be a funeral that anyone other than the immediate family can attend, so this is the only way that House members can pay their respects to Officer Sicknick and honor his sacrifice.