With DUI, forget about F1, a GreenCard holder can be deported too.
He may have got deported because of DUI, NOTHING TO DO with Government signing SB4 which is taking effect on Sep 1, 2017. He signed this law to remove Texas cities from sanctuary city.
What this means is, if you are arrested or even detained, a police officer can ask you about your legal status. However, before this law gets into affect, the officers are not allowed to ask about the status of anyone they detained as a part of the SANCTUARY CITY. (Dallas being one of the sanctuary city)
Again, it doesn't mean you are arrested = you are deported.
As always, be safe.