Denali not starting up.help

[LOWHOE775]

I'm trying to help my buddy out. He has a 00 Denali with the 5.7 vortec. It is the obs and for some reason one day he went to work and left the visor mirror light on an his battery died. When we went to jump it, it cranked but it did not fire up. So we swapped out the battery for a fresh one and did not fire. Any ideas on what is wrong with it. The fuel pump is working. Any help would be Appreciated.

 

[SunlitComet]

How is his security light acting when going thru all this?

 

[LOWHOE775]

I do not know but I will check it out today after work. What is it suppose to do?