Jan Hendrikx studied in Nijmegen and was involved in student resistance there before returning to Venlo and becoming a teacher. , p. 576
In 1940, J.J. Hendrikx (pseudonyms Ambrosius and Giel Gabrielsen)  began helping escaped French prisoners of war. In 1941-1942 he became involved in the care of Jews.
Through these activities he came into contact with the LO. 
Became district leader of LO-Venlo until the second half of the summer of 1943, when he switched to leadership of the entire LO region and the national organization. , pp. 500-501 and 579
He was also the contact person for the NSF in the province of Limburg. 
The NSF (National Support Fund) financed aid for families of sailors on Allied ships, and later also for families of people in hiding and the financial needs of resistance groups. 
Ambrosius and with him almost the whole top of the regional L.O. were arrested on June 21, 1944. This was during a meeting of the district leaders of the LO Limburg in Weert. This catastrophe has become known as the Raid of Weert
They were taken to the Vught concentration camp. When Vught was evacuated in early September 1944, Hendrikx was transferred to Sachsenhausen concentration camp. As the Russians approached, the Germans transported their prisoners to Neuengamme. During this transport, J.J. Hendrikx succumbed to exhaustion in early February 1945.  
Dr. Fred Cammaert said during his speech at the unveiling of the plaque  next to the Peace carillon: The second one I want to mention is the teacher Jan Hendrikx from Venlo. At the request of the chaplains Naus and Van Enckevort, he took over to build up the Limburgian hiding organization LO in 1943. He traveled towns and countryside and made numerous valuable connections both within the province and beyond. He also belonged to the leadership of the national LO. And like the clergy involved in the resistance, he was an outspoken supporter of nonviolent resistance. During the Raid of Weert on June 21, 1944, he fell into German hands. He was killed in early 1945 during one of the cruel evacuation transports of camp prisoners. See also the Death marches  of concentration camp prisoners at the end of WW II.
Bearer of the Verzetskruis 1940–1945  (Cross of Resistance, one of the highest awards in the Netherlands, was awarded only 95 times)
He is listed in the “Erelijst 1940-1945” (Honor Roll of the Dutch Parliament).