There are so many things that are wrong in the movies with which tributes get killed and which don't, and I'm not comparing them to the books because I haven't read them.
In The Hunger Games, you can clearly see on the map in Day Two that a tribute from District 10 is walking near the Cornucopia, along with both from D11, one from D5, and one from D3. We know that D3 is the boy who Cato kills later. D11 are Rue and Thresh. D5 is Foxface. However, D10 is problematic. We see D10 male get killed (hard) in the bloodbath. We never see the D10 girl, so it could be her. However, she is in the background behind Caesar as one of the fallen. So there's clearly some editing problems with the film. Also, at the end of Day One, there are no fallen tributes from D10 shown in the sky, and they go in numerical order. At least one has to be dead, as in Day Two, there are 11 left after the D8 girl is killed by Glimmer. Caesar then says, 13 dead in 8 hours. The 11 remaining are confirmed a few minutes later by the overhead of the arena map - D1, D1, D2, D2, D12 (Peeta) moving towards D12 (Katniss), and the others I mention above near the Cornucopia. So, either D10 girl is still alive and they messed up both the fallen tribute video at the end of Day One (AND) the pictures of the fallen behind Caesar, or D10 boy was not killed in the bloodbath (somehow), and D10 girl was. That would mean that they still messed up the fallen tribute video because D10 girl wasn't shown at the end of Day One, and we know only 12 survive Day One, because Katniss hears 12 cannons, and after D8 girl dies, Caesar confirms there are 11 left. This is the first issue.
Next, we know that Thresh is killed by the mutt dogs, because we hear him screaming in the distance with the snarling and growling. He's immediately shown in the sky after he dies. Cato did not kill him. However, in the film Mockingjay Part 2, Katniss says that she killed Cato, he killed Thresh, Thresh killed Clove, etc. Clearly, they forgot what happened in the first movie. This is another issue.
In Catching Fire, at the bloodbath, Peeta DOES NOT fight and kill the male from D9. This is a big error on the filmmakers' part. I've slowed it down frame by frame because it never looked like the D9 male to me. The D9 male was the biggest guy out there except for Brutus. He was much bigger than the male Peeta killed, and had longer hair. When you slow it frame by frame, it is the D10 male (or at least the actor) that Peeta defeats. Now, either they messed up, and meant for it to be the D9 male actor, or they put the wrong fallen tribute victim in the sky at the end of Day One. I believe the book had Peeta kill the D9 male in that sequence, but it is definitely not him in the film. That's the first issue.
The second issue with Catching Fire is that there is only one cannon fire after Johanna kills Cashmere. Eight are killed on Day One (according to the tribute video in the sky) - D5 male, D6 male, D8 male, D8 female, D9 male, D9 female, D10 female, and D11 female. Again, D9 male not withstanding, this could be accurate. That leaves D1 both, D2 both, D3 both, D4 both, D5 female, D6 female, D7 both, D10 male, D11 male, and D12 both for a total of 16.
On Day Two, there is NO cannon fire after the lightning hits the tree for the first time, nor is there one before or during the fog sequence until Mags sacrifices herself. So NO ONE dies on Day Two (in the film) before Mags. Then D6 female, and D5 female. There is NO cannon fire to indicate that D7 male has died, though Johanna tells the group on the beach after they come out from the woods. So, no cannon fire is another error (won't be the last.) Then Wiress is killed by Gloss, who is killed by Katniss, and Cashmere is killed by Johanna. That's 7 deaths on Day Two. However, the end of the day confirms all of these, plus D11 male, though there was never any other cannon fire, nor any indication in the film of when/where/how he died. If there was a cannon fire, at least we could know when, but there wasn't.
On Day Three, we know the following are left (8 total) - D2 both, D3 male, D4 male, D7 female, D10 male, D12 both. We know this is true because we see all of them in the film except for D10 male, but he is not in the fallen tribute video at the end of Day Two. Again, we NEVER hear another cannon fire leading up to the confusion at the end. Johanna helps to fake Katniss' death to distract Brutus and Enobaria away. Beetee gets zapped by the force field, and Peeta is nowhere to be found. D10 male is still unaccounted for, and Finnick arrives back at the tree looking for Katniss. We do hear a single cannon fire at this point, but don't know who it's for. Given that Johanna, Enobaria, Finnick, Beetee, Katniss, and Peeta are in the next two films, that leaves Brutus, and the D10 male.
There is NO reason to think that Peeta killed Brutus in the film, as we never see Peeta during that final sequence, and Johanna is leading the D2 pair away from the tree and Katniss. So, the conclusion is that it's for the D10 male.
These are just some of the observations I've made and wrestled with after watching them several times. There's nothing more frustrating then when the editors leave something out or get it wrong and don't catch it. I could certainly live with them not showing every death, but there should NEVER be a glaring contradiction when the editing is done, nor should they leave out critical things like the cannon fire when it's so heavily emphasized during the first two films (and even in Mockingjay Part 2 when they assume the assault team is all dead and show the video with cannon fire.) It's simply not excusable.
I just wish people would stop making illogical conclusions about the fate of Brutus because there's no reason to believe (in the film) that he died at all.