The man, identified as Ethan Courrau, is considered the suspect in the stabbings and died Wednesday night after being hospitalized with serious injuries, sheriff's spokesman Lt. Jeff Kramer said.
The children are Scarlett Kayne, 1, and her brother Ryan Willhite, 3, Kramer said, adding Courrau was not related to the children but had some association with their family.
The incident occurred at a former equestrian stable northeast of Colorado Springs, Colo., the Colorado Springs Gazette reported Thursday.
Kramer said investigators were uncertain if Courrau's wounds were self-inflicted, noting: "That's something we are looking into. It's still under investigation."