Sources? Googling both only disproves both your claims.
Murders certainly increased markedly in major cities in 2020.
Regardless of the extent that the increase is due to statistical noise or socio-political factors: it is obviously incorrect to look at one deeply unusual year and proclaim the trend is “reversed.”
To parent's credit, the CDC did report a decline in life expectancy at birth from 2014 to 2017, but the decline was of of a couple decimal points total, which is well within standard error.