Found Guilty hi ShootingBy a Staff WriterWATERLOO, 1A. —A Black llawk Cofinty District Court jury, deliberated only a half-hour Thursday afternoon before finding James E, Walker, 23, of Waterloo, guilty of shooting a service station attendant here last March.Walker wilt be sentenced at11 a.m. Aug. 20 on the conviction of assault with intent to commit murder.He was accused of entering a Holiday Service Station on La Porte road on Mar. 12, forcing the attendant, Mark Covington, 24, of Cedar Falls, to give him $30 from a cash register and then shooting Covington in the head, causing him.to lose vi- * sion in his right eye. «In 1964, Walker was given a I suspended 25-year prison sen- i 1 Itence after he was found guilty ■. of participating in a $200 armed * I holdup of another service sta* j |tion here, according to police;! ivcnfits