The article says he was open about his Jewishness, so I presume it means he was wearing the yarmaluk.
The article says he was wearing a skullcap, but was not wearing any other distinctively Jewish garb. He was clean-shaven. A Modern Orthodox-type yarmulke would seem barely noticeable.
Most religious Jews are open about their Jewishness faith and wear religious garb in devotion to it. Are Catholics who wear a cross said to be "openly Christian" just because they wore a religious symbol unique to them?
I reject the notion of replacing one's expression of faith as being "Jewishness" or "Christianness" or "Musllimness" or whatever. The police officer and/or the writer of the article were being lazy in their description of the individual. Devotion to a creed or faith is just that; both of them could just as easily said the man was "openly devout" instead of calling him "openly Jewish."
"Openly Jewish" implies that it is something best kept in private.
-PJ