Police in Texas are searching for a stout black man in his 30s or 40s who is suspected of sexually assaulting at least four women in cities and towns near Dallas. The common thread? His victims, now in their 50s or 60s, were all members of the same sorority, Delta Sigma Theta. A Plano police spokeswoman said the assailant “made it obvious to our victims that he knew information ... about them personally,” and none of the women believe they had known him. In each case, he entered the women’s homes overnight when they were alone. The national Delta Sigma Theta organization has issued a warning to all alumnae in the Dallas area.