The only window in the building was in the entry door, and had steel bars over it.
The criminals cut the bars.
No word on if they were clearly shown on video.
According to the report on Fox, there was a delay after the alarm went off before police were called.
Then of course the delay before they could get there (no Star Trek transporter).
I'd guess the criminals probably had close to 10 minutes, which even with cutting the bars on the door gives them lots of time. The door they chose faces the street, though there are other doors which don't, so if the least secure option was the door w/ bars, I don't fault the shop for their choices.
From what I've heard on the news (yeah, I know how inaccurate that can be) it sounded like they targeted the cases closest to the door; the reporter (or maybe the detective, I don't remember) said something about that they mostly got .22's.
So other than knowing that they needed to cut the bars, I don't think they cased the store at all, otherwise they'd know how the merchandise was arranged.