Kathlynn Shepard Missing: Authorities also probe suspect Michael Klunder in 2012 slayings of Iowa cousins Lyric Cook and Elizabeth Collins

(CBS/AP) IOWA CITY, Iowa - An Iowa police chief says a dozen investigators are looking into whether Michael Klunder, the suspect in Monday's kidnapping of two girls, is connected to last year's slaying of two young cousins, Lyric Cook and Elizabeth Collins, who vanished 90 miles away.

PICTURES: Bodies of missing Iowa cousins identified

Authorities believe Klunder kidnapped 15-year-old Kathlynn Shepard and her 12-year-old friend as they walked home from school. The 12-year-old was able to escape, but Kathynn is still missing.

Evansdale Police Chief Kent Smock said Thursday that investigators are now scrutinizing Klunder in connection with the deaths of Lyric Cook and Elizabeth Collins because of similarities in the two double-kidnappings.

The cousins were 10 and 8 when they disappeared while riding bikes last July. Their bodies were discovered in December.

Smock says investigators are "exploring anything and everything" about Klunder, who police say was found dead earlier this week from self-inflicted injuries hours after the 12-year-old escaped.

According to police, Klunder has a long criminal history and was ordered for sex offender treatment when he was a teenager.

It was previously reported that Cerro Gordo County Sheriff Kevin Pals called Klunder "a creep" who once kidnapped a 21-year-old woman and two 3-year-old girls.

Police are continuing to search for Kathlynn, specifically around Dayton, about 60 miles north of Des Moines.

Complete coverage of Lyric Cook and Elizabeth Collins on Crimesider

Complete coverage of the Kathlynn Shepard abduction on Crimesider