I think these refugees/migrants were from Niger and Liberia. Many try to get to Europe across the Med via Libya and Algeria.

I met an Algerian security guard in a Nike shop in Norwich at the weekend. We chatted in French about the football and he was very amicable. But when my husband came up (he'd been paying at the till) he suddenly turned hostile and dismissive.
My husband explained later that North Africans often regard black Africans as inferior and 'primitive'.
I wonder if this explains to some extent their callous treatment of the
refugees.
The poor souls had probably paid 'traffickers' to get them into Algeria, and then they died of thirst and exposure in the Saharan sand.
Heartbreaking.