According to a post upthread he came to the US in July 2009. Then there was the rape allegation in 2014 -
A northern Utah police department says it investigated a rape allegation five years ago against a man suspected of killing a Salt Lake City college student, but say the alleged victim declined to pursue charges.
The Latest: Suspect in Utah killing had been accused of rape
I suppose the allegation/incident could have happened just after he got his citizenship, but if he could only start the process when 5 years residency was up, the timing does seem tight, presuming that he came to the attention of LE at that time.