TAMMS, Ill. -- A man who police say strangled his wife before being gunned down by a sheriff's deputy spent weeks saying farewell to relatives while displaying erratic behavior involving a sword and biblical hallucinations with his spouse, one of the man's sisters said Friday.

Belinda VanDommelen said she believes her 48-year-old brother, Bobby Curtis, and his wife had discussed ending their lives before they died July 26. Curtis was fatally shot in Tamms after a car chase by an Alexander County sheriff's deputy authorities say he threatened with a sword. Investigators found the body of Lisa Curtis, 50, in the passenger seat.

VanDommelen said the couple, who died two days after they walked away from a mental-health evaluation, had been tormented since the 2005 death of 17-year-old son Jeremy Curtis. The teen was hit and killed by a motorist as he walked in Panama City, Fla., the resort town where the family lived.

Illinois State Police told KFVS12 in Cape Girardeau that powder found in Bobby Curtis' car tested positive for the synthetic drug "bath salts" that mimic cocaine, LSD and methamphetamine. Toxicology tests are pending to determine whether the couple had taken the drug, which can cause chest pains, increased blood pressure and heart rate, agitation, hallucinations, extreme paranoia and delusions.

"All they ever wanted was to be with their son Jeremy," VanDommelen said by telephone Friday from her home not far from where her brother was shot. Since Jeremy Curtis' death, "they've never been the same, crying every day."

The couple had other misfortunes, losing a son at birth and seeing Bobby Curtis' contracting job in Panama City wither after last year's BP oil spill in the Gulf of Mexico pummeled that region's tourism industry.

In the days before they died, VanDommelen said, the Curtises "were delusional, confused," speaking in biblical terms and of demons.

"They saw angels and writing everywhere," VanDommelen said. "They stated the clouds were talking."

On July 24, VanDommelen said, Bobby Curtis used a buck knife to hack off his braided ponytail, muttering that he had to sacrifice himself to go to hell to get his dead teenage son and his father, who the couple thought was God, and "get them to heaven."

A deputy took the couple that day to the sheriff's department in Alexander County, then eventually to a nearby hospital for psychiatric evaluation. The Curtises soon fled after being allowed to go outside to smoke cigarettes.

VanDommelen said the couple turned up at her house the next night and were allowed to stay, only to be told by VanDommelen's husband early the next morning that their erratic behavior -- "they were screaming out, saying, 'Get the demons out of me"' -- no longer was welcome.

"They told him it was Judgment Day," VanDommelen said, noting Bobby Curtis was at the time clutching a sword, insisting "he was the Alpha Omega, Jesus Christ."

The sword, VanDommelen said, was among those the Curtises' late son had collected.

Later that day, Curtis led a sheriff's deputy on a chase that ended when he crashed his car near Tamms. Illinois State Police said Curtis emerged from the vehicle wielding a sword, first using it to try to injure himself before threatening the deputy who ultimately shot him. Curtis died later at a hospital.

Illinois State Police on Friday announced plans to hold a Tuesday news conference about the case. Messages left with Alexander County's sheriff were not immediately returned.