Yashamaru is the care taker and only friend of Gaara. He was ordered by Kazekage to look after Gaara and to protect him as well (as if Gaara needs any protection). Yashamaru gets hurt when defending little kid's from Gaara. Yashamaru's sister was the mother of Gaara, and because of the curse Gaara has embedded in him, Yashmaru's sisters' life had to be sacrificed for the curse to work.
This protector of Gaara also explains that flesh wounds may hurt but they are easy to heal and medicine will speed up the process of healing. The other kinds of wounds are wounds inside your heart. Some may heal over time, some of them will last a lifetime. The only thing that can heal the wound of the heart is love. The caretaker tells Gaara that he has received this love from his (Yashamaru's) sister. He thinks that the sand protecting Gaara is the love of the mother.
Yashamaru is later ordered by Kazekage to kill Gaara as he is getting out of hand. He shows up in a face cover and attacks Gaara in the back. Of course the sand protects Gaara and he defeats Yashamaru with minimal effort. Gaara removes the face cover to realize his attacker was his only friend, Yashamaru.
The ninja of the sand explains that although on the surface he tried to like Gaara, but deep down he has always hated him. Yashamaru opens his jacket to reveal about 20 burn notes on his chest which catch on fire. His finals words are: "This is it. Please die."