Come dusk, he will often stumble upon the border crossers themselves.
The Latinos, more than other immigrants, are frequent border crossers.
Seventeen border crossers have died in the area around Douglas during the last four and a half months, compared with 18 during the previous 12.
Rules include not speaking to, approaching, gesturing towards or having physical contact in any way with any suspected border crossers they may see.
In recent years, several agents have also been convicted of assaulting border crossers and other abuses.
But the Chinese government also orders periodic sweeps and repatriation campaigns, sometimes for political reasons or when the number of border crossers becomes too big.
But border crossers are a resourceful lot and they'll keep probing.
Patrolling Swiss frontier guards intercept perhaps only 10 percent of the border crossers.
The border crossers pouring into Arizona a decade or two ago were more numerous, but less likely to be threatening.
The series "Tangenten" was specifically introduced to promote such "border crossers" between cultures and nations.