TOULON, Ill. -- The man who was shot after authorities say he killed a sheriff's deputy and a neighbor couple remained hospitalized on a respirator Sunday while investigators considered homicide charges.

State trooper Jeff Darko said police may not be able to piece together why Curtis Thompson, 60, shot his neighbors Friday night unless his condition improves. Thompson is accused of shooting and killing James and Janet Geisenhagen, 43, after he shot and killed Stark County Deputy Adam Streicher as he was serving an arrest warrant.

Neighbors in the central Illinois community of 1,300 residents have described Thompson as unfriendly and aggressive, and said he has carried on a feud with the Geisenhagens.

"Currently there's speculation from the townspeople and relatives of the Geisenhagens and no one really knows the motive except Mr. Thompson," Darko said. "If the medical condition of Mr. Thompson changes, then maybe we'll know why he did this."

He said the investigation was continuing.