ya mugía por su frente 
a las cinco de la tarde. 

This may sound like the obvious way to treat a tragic reality such as death, but Garcia Lorca emasculates death in order to superimpose the greatness of manhood, gentleness, and character of Sánchez Mejías. This, he does in part 2, "La Sangre Derramada", where he focuses on the actual passing of Ignacio, on Lorca's own despair, and  on the unfair loss that both Lorca, as well as Spain, will feel with the death of a Gran Hombre. Look in the following stanza how you can almost hear Lorca's tears as he relates the situation:

Por las gradas sube Ignacio 
con toda su muerte a cuestas. 
Buscaba el amanecer, 
y el amanecer no era. 
Busca su perfil seguro, 
y el sueño lo desorienta. 

One can even suggest that García is angry at the fact that death has come to take such a great man; so angry, in fact, that he insults death and declares that he refuses to look it in the eye as if he had to welcome and accept it. You can find this also in part 2. 

¡Quién me grita que me asome! 
¡No me digáis que la vea! 
No se cerraron sus ojos 
cuando vio los cuernos cerca...

However, the most important thing that García does is to take away the element of mysticism out of death. This is found in part three "Cuerpo Presente", where Lorca gives a very emotional rendition of what is a great man. Again, he superimposes man over death:

Vete, Ignacio: No sientas el caliente bramido.
Duerme, vuela, reposa: ¡También se muere el mar!

This phrase "¡También se muere el mar!" may very well represent every sentiment in the heart of García Lorca: he wants so badly to farewell his friend, but he is so heartbroken, angry, and desolate that he just cannot let him go easily. He wishes his eternal repose, but refuses to accept that death has come.

By saying "tambien se muere el mar", Lorca is remiding himself how the waters, in their cycle, come to a re-birth at all times. If death cannot beat the seas, and seas exist forever, then what could death possibly do to the memory of Ignacio?

The final part of the poem, "Alma Ausente" has one specific stanza that voices Lorca's tears in their entirety and it is when he says

No te conoce nadie. No. Pero yo te canto. 

Just imagine: at the time of someone's untimely death, the great Garcia Lorca singles you out from the rest of the world and says "yo te canto". That is no small honor. That is literally defying the role that death is mean to take in an elegy: Lorca no le canta a la muerte, le canta a Ignacio. The time and effort that he takes to do this is what makes this poem so amazing.

Here's a link to the English translation of the poem as well if you need it: http://allpoetry.com/poem/8512753-Lament_For_Ignacio_Sanchez_Mejias-by-Federico_Garcia_Lorca