Updated

Investigators said Thursday that letters sent to police and a television station appear to be the latest communications from a serial killer who resurfaced this year after more than two decades of silence.

Wichita police received a letter earlier this month describing the 1974 strangulation of four family members — the earliest of eight deaths for which the killer known as the BTK strangler (search) has claimed responsibility.

"We truly feel that he is trying to communicate with us," police Lt. Ken Landwehr said.

The FBI has also confirmed that a letter received by Wichita television station KAKE, turned over to police on May 5, is an authentic BTK communication, Landwehr said.

The BTK killer — the letters stand for "bind, torture, kill" — terrorized Wichita in the 1970s, bragging about seven slayings in letters to the newspaper and television stations.

On March 19, a letter from the killer arrived at The Wichita Eagle with information on an eighth unsolved killing in 1986. That letter contained a copy of the victim's driver's license and photos of her slain body.

The letter sent to KAKE last month contained a puzzle and photocopies of employee identification cards for two men: a former Southwestern Bell worker and a former employee of the Wichita public school district.

Police believe the killer may have used the IDs to gain entry to homes.

The names on the cards have not been released. But in an interview with KAKE, the former Southwestern Bell employee said he had no idea why his business card would have been in the letter. The school district said the name on its card was similar to that of a past employee, but title of "special officer" on the card does not exist.

"He is taunting the police, obviously," said Steven Egger (search), an associate professor of criminology at the University of Houston-Clear Lake and the author of three books on serial killings. Egger speculated the taunting means the killer is "very likely" to strike again.

Scott Thornsley (search), a criminal justice professor at Mansfield University in Pennsylvania, said the killer may like being at the center of attention again. "He has gotten away with the crimes for 20 years and now he is probably America's most sought after serial killer. That makes him feel important," Thornsley said.

Since BTK resurfaced, police have received more than 2,200 tips and leads.