Here it mentions Liz being part of Make-a-Wish foundation and performing in hospitals for sick kids.
Elizabeth Barraza — Unresolved
Her parents’ site mentions Liz Barraza’s Harry Potter Library in children oncology ward. Ms. Martinez was a volunteer teacher in an elementary school. Honestly, this is the first thing that comes to mind.
I paid attention that Mr. Martinez took his life less than a month after Ms. Martinez got shot, poor man. Probably, his heart was broken, but a totally different question regarding Barraza/Martinez connection formed in my head, i.e., could the cases be linked via a third person. It is probably my overactive phantasy.