Wichita ? Investigators said Thursday they believed a pair of letters sent in the past two months were from the BTK killer.

Wichita Police Lt. Ken Landwehr said police received a letter earlier this month describing the 1974 strangulation of four family members. They are the earliest of eight deaths for which the killer known as BTK — the letters stand for “bind, torture, kill” — has claimed responsibility.

On Jan. 15, 1974, three children of Joseph and Julie Otero came home from school to find their parents and two siblings, Josephine, 11, and Joseph II, 9, dead at the family’s home.

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

“We truly feel that he is trying to communicate with us,” Landwehr said.

A letter from the killer that arrived March 19 at The Wichita Eagle with information on an unsolved 1986 killing has reignited public fears in the state’s largest city. That letter contained a copy of the victim’s driver’s license and photos of her slain body.

It was the first communication from the killer known as the BTK Strangler in more than two decades, and police said it linked BTK to an eighth slaying. BTK terrorized Wichita in the 1970s, killing seven people and then taking credit for the deaths in letters to the newspaper and television station.

“He is taunting the police, obviously,” said Steven Egger, an associate professor of criminology at the University of Houston-Clear Lake and the author of three books on serial killings.

BTK may be after recognition, Egger said, noting that most serial killers look like the average person on the street.

“He may be an individual who hasn’t gotten a lot of attention in life,” Egger said. “This is the way he gets attention.”

By describing to police in a letter the 1974 murders of the Otero family, the killer is to some extent reliving a fantasy, Egger said.

Egger said BTK was “very likely” to kill again if he is taunting police.

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 an employee of the Wichita public school district.

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

Based on the information in that letter, police are asking for information from anyone who remembers someone trying to gain entry to their home using a school or utility identification between 1974 and 1986.

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

It is surprising he is providing police with leads, said Scott Thornsley, a criminal justice professor at Mansfield University in Pennsylvania.

“But what this is accomplishing, perhaps, is that everybody is talking about the case again and he is the center of attention,” Thornsley said. “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.”