Theo Boonen was a farmhand. During the last winter of war, some young people, including Theo, decided not to be evacuated and to go into hiding in the barn of the Moors family.
Around Jan. 26, 1945, he was arrested in the kitchen of the Moors’ home by paratroopers of Major Ulrich Matthaeas’ battalion as he was busy collecting food. The other six people in hiding were also arrested in the following period 
They were considered terrorists. It is not made clear why he is not considered a resistance fighter by 4en5mei.nl , although his friends, the Jacob and Jan Moors brothers, are.
For more information go to: Herten.
Listed on the Oorlogsmonument (war memorial) Roermond. 
gevallenenroermond.nl/ writes: “Shot 16 April 1945, place unknown.” 
He is listed in the “Erelijst 1940-1945” (Honor Roll of the Dutch Parliament).