22-year-old Carli Richards -- whom Holmes shot in the back with a shotgun -- tells TMZ, "I think death by firing squad would be totally justified ... Just injecting him is painless."

She says, "I had enough needles in me that night to know that a needle isn't that bad. I want him to see what it feels like ... I wish someone would shoot him and let him bleed out."

She adds, "He shot me with stuff they use to shoot birds and deer. I want him to feel what it's like to feel that helpless."

Thankfully, Carli and her boyfriend made it to safety before Holmes could kill them -- but Carli says she's still in a lot of pain, and can't go back to work yet with her current injuries.

Carli is the second person affected by the massacre to call for Holmes' death. TMZ broke the story yesterday, the husband of a woman killed in the shooting also demanded the death penalty.

It's worth nothing because prosecutors have said they will only consider pursuing the death penalty with support from the victims' families.

Holmes was charged Monday with 142 crimes stemming from the Colorado shooting -- including 24 1st degree murder counts, and 116 counts of attempted murder.