The opening title cards: "One out of every twenty-one Black American males will be murdered in their lifetime", followed by "Most will die at the hands of another Black male." All this is played over the intense sounds of arguing, gunshots, children screaming, and one child crying, "They shot my brother!" Cue the opening shot of a STOP sign. Some Anvils Need to Be Dropped, indeed.
Tre visibly fearing for his life at the hands of a police officer. His subsequent emotional outburst in front of his girlfriend will definitely get the waterworks going.
Doughboy's mother's treatment of him from him and Ricky getting into a fight to after Ricky's murder for the death.
Worse is Doughboy telling Tre his mother wants nothing to do with him anymore after Ricky's death. Fridge Horror sets in when you remember she (inadvertently) lead him down that path of destruction and later on would lose him as well.
Ricky's death was probably all the more worse for Doughboy when you consider the very last interaction the two brothers shared was an acrimonious brawl.