Normally, there would be indications or statements that there was no known contact between the victims and the suspect.
Other articles state the police are not releasing any information at this time.
If he didn’t know them or never worked for them, it may have been the authorities tracked him down via DNA.
My guess is the bloody hand print on the door. Fingerprint probably matched those taken at the time of his arrest in Grayson Co. and previous deportation.