Good question. I doubt they arrest many since the information isn't available. Like this guy, they release him. I'm surprised there was follow up. This certainly isn't the way to protect the country. I don't blame for the border agents for that.
As to this guy I assume we'll go through the deportation process, which will take several years and cost well more than $100,000. He'll probably get representation from some non profit, if not we'll pay for his attorneys.
That said, this guy was stupid. Presented himself to agents presumably using his real name. From the little I know of Senegal they have significant political unrest, many protests due to the holding of political prisoners. For all I know he may not be a terrorist but legitimately being politically prosecuted. I guess our system will work that out in this case. This one case. He could be one of the 25,000 or so of the millions Joe is encouraging to come here that actually receive asylum.
Or he could be a legitimate terrorist and we caught one. Rest assured the terrorists coming from established groups are hiking through the desert to their US contacts with fake id.
He will.
As a legitimate terrorist, he has reasonable fear of persecution back in Senegal...