When you think about it, Danny Rolling's murder victims were partly just due to opportunity. Sleuthers want to find a connection and a prior motive to these killings, but like you say, sometimes they're random killings due to there just being an opportunity. Like this case I posted about before that happened in 1992.
PLEASE READ THIS WHOLE NEWS ARTICLE.
A college student who found her roommate brutalized in their rented home near campus said the University of Idaho slayings have rekindled memories of the savage attack.
www.foxnews.com
Two surviving roommates, who lived on the basement level, appear to have slept through the carnage that occurred on the second and third floors.
Police have not identified a suspect or recovered the fixed-blade knife they believe was used in the ambush.
In the 1992 case, Zabel and her roommates attended a Sigma Chi party – just as Kernodle and her boyfriend, Chapin, had the night before they were murdered.
[...]
"We always assumed it was a fraternity brother. We couldn't get out of the box of thinking it was someone we knew," she recalled.
Take Note-- Well, it wasn't a fraternity brother or anyone in their social circle. It was just a criminal taking advantage of a random opportunity of an open window. Sometimes it's not a stalker or a targeted crime, but just taking advantage of the opportunity of an unlocked door or window.
BBM & UBM