customs area at the border crossing. police blocked them there. they then tried to walk along the tijuana river to where it intersects with the u.s. border. they were there for a while. and at the very bottom of the tijuana river, at that point there s an earthen levy with three strands of stacked wire. eventually some of the migrants began to filter down to that area at the bottom and there s a small gap where the water trickles through. and interviewing a family who was down there at the time, i was up on the side of the river watching. they said that some of the migrants opened a small hole in the wire and that s when the u.s. agents began firing tear gas. i saw at least half a dozen, maybe ten canisters launched into mexico. the breeze was carrying into mexico. so we were running for several minutes to get out of the cloud