photo credit: Hospitalfield
This work is entitled 'A Scene of Rebellion'. It appears to show people being executed in the middle of a busy street in a Flemish town. However, if you look at the general calmness of the scene, with housewives coming out of their homes to watch and a crowd of people standing behind the people being shot at, it is clear that this is not a violent scene. Rather, it depicts one of the parades of the local militia which included demonstrations of firearms using only powder. A similar scene can be found in Denys van Alsloot, 'The Ommeganck Procession in Brussels on 31 May 1615: The Senior Guilds' in the collection of the Victoria and Albert Museum. In the centre of that painting we also see demonstrations of firearms. https://bit.ly/2x7N4zl
Nicolaas van Eyck was himself a member of a local ‘schutterij’ (civil militia) and is known to have painted parades of local militia in his home town Antwerp. An example is in the Museum Vleeshuis, Antwerp. https://bit.ly/2xcAePE
Further evidence for this being a representation of a parade of a civil militia can be found in the (unfortunately poor quality b/w) reproduction of van Eyck's 'Grote Parade van de Antwerpse Burgerwacht op de Meir, 1673' (Grand Parade of the Antwerp Civil Guard on the Meir, 1673). https://bit.ly/2p4Oq9X On the far right of this canvas is depicted a row of militiamen shooting at a few men with their backs turned towards the shooters. The three houses depicted on the right-hand side are almost identical to the three houses depicted in the Hospitalfield painting. It is therefore likely that the Hospitalfield painting was originally part of a larger depiction of a parade of the Civil Guard on the Meir - the principal thoroughfare in Antwerp. This larger canvas appears to have been cut up and the Hospitalfield painting may be the sole extant portion of the original work (unless an art detective can locate other pieces of it ...).
The two large van Eyck's paintings in the Antwerp Fine Art Museum and the Museum Vleeshuis are clearly 'versions' of the same 1673 event: the general groupings, individual figures and poses, are practically the same, as well as the setting. This painting also clearly shows the same buildings on the right hand side, with slight differences of detail (e.g. lacking a rear chimney projecting above the centre of the roof on the right, and with a perspectivally odd left-side addition to the tall one at left). Irrespective of whether it is a cut-down fragment or not the title should perhaps be changed to something like 'A militia parade and musket demonstration on the Meir, Antwerp'. I have an imperfect memory that the technical Dutch term for this type of subject is a 'schutterstucke' (?), of which Rembrandt's 'Nightwatch' is the most famous, but someone can perhaps correct my spelling at least