What was the departure of Boxer like?

In Chapter Nine, Boxer lies in his stall and takes doses from “a large bottle of pink medicine” that the pigs send from the farmhouse. He expresses his wish to spend his final years learning the rest of the alphabet. One afternoon, a van comes to take Boxer away. It has “lettering on its side and a sly-looking man in a low-crowned bowler hat sitting on the driver’s seat.” The hopeful animals wish Boxer goodbye, but Benjamin breaks their revelry by reading the lettering on the side of the van: “Alfred Simmons, Horse Slaughterer and Glue Boiler, Willingdon. Dealer in Hides and Bone-Meal. Kennels Supplied” (123). The animals panic and try to get Boxer to escape. He tries to get out of the van, but he has grown too weak to break the door. The animals try to appeal to the horses drawing the van, but they do not understand the situation.