PHOTO! Here is a picture of alleged Los Angeles westside rapist John Thomas Jr., 72. John Thomas is Los Angeles’ worse serial killer ever, claim police today, making their arrest nearly 3 decades after a police hunt began.

Police are holding Thomas in two killings but claim he might be responsible for as many as 30 persons’ deaths, nearly 10 years apart.

Police for decades have tried to solve the crime. The West Side rapist started in the 1970s and would at night attack and kill elderly women. 10 years later killings started up similar in Claremont.

Why the sudden arrest? DNA claims police. Reports Newsday:

The break came last October, when two officers collected DNA from Thomas as part of an ongoing process to swab registered sex offenders. On March 27, the California Department of Justice DNA Laboratory notified detectives that his DNA matched the evidence from the Sokoloff slaying.

On March 31, they were told that his DNA matched the four other slayings. He was arrested later that day. Thomas is being held at L.A. County Jail and could not be reached for comment.

Thomas is now 72.