OR c.) he was named by someone who wanted him known to police.
You're right - the reports of today's testimony made me think it was some covert operation of LE 'putting out feelers' about someone with that tattoo, but in fact from the Hamilton Police facebook page, they publicized the tattoo on the morning of the 10th, by later that day they had information from two people identifying DM. That same day they went to visit him, and perhaps as soon as they had his cellphone data from the night of the 6th, they arrested him.
So the 'police sources', that I took to mean people who regularly report to police, were probably just tips from people who knew DM. I recall now, it was very public information and DM must have heard about it.