thumbtacks in Central Park?
I exprienced something similar in the woods a few years back
got a double flat
felt it was suspicions
shared this notion with my brother who also would visit these trails
he shortly after got a double flat
he returned to those trails with a MD Police officer who had a metal detector
that officer found a ribbon of tacks set as a trap
I think I may have found reference to my own mention of this!
but not this