You are probably remembering District 9 (2009).
The film is partially presented in a found footage format by featuring fictional interviews, news footage, and video from surveillance cameras.
In 1982, a giant extraterrestrial spaceship arrives and hovers over
the South African city of Johannesburg. An investigation team finds
over a million malnourished aliens (derogatorily called "Prawns")
inside, and the South African government relocates them into a camp
called District 9. However, over the years it turns into a slum, and
locals often complain that the aliens are filthy, ignorant lawbreakers
who bleed resources from humans.
Following unrest between the aliens and locals, the government hires
Multinational United (MNU), a huge weapons manufacturer, to relocate
the aliens to a new camp outside the city. Piet Smit, an MNU
executive, appoints his son-in-law, Wikus van de Merwe, to lead the
relocation. Three aliens, Christopher Johnson, his young son CJ and
his friend Paul, search a District 9 garbage dump for an alien fuel,
which after twenty years Christopher finally has synthesized enough to
enact his plan. But when Wikus comes to Paul's shack to serve him
notice, Wikus finds the hidden liquid container and accidentally
sprays some of it in his own face while confiscating it. Paul is
executed by Koobus Venter, a cruel MNU mercenary.
Wikus begins mutating into an alien. He is taken to the brutal MNU
lab, where researchers discover that his chimeric DNA grants him the
ability to operate alien weaponry.
There is a scene in the movie that shows people killing and eating aliens them in an attempt to become aliens and use their weapons. As mentioned above, the main character slowly becomes an alien, not from eating them, but from accidentally spraying himself with a liquid from a container. The same people also attempt to eat the main character, as he achieved their goal of transforming into an alien.