A Woodacre man arrested for leaving explosives in front of his estranged wife’s house is facing new charges that he told fellow inmates he would kill the woman after his release, Marin and Sonoma County law enforcement officials said. Mark VanMidde, 49, was declared mentally incompetent to stand trial during a hearing held by Judge Jamie Thistlethwaite on Wednesday in Santa Rosa. Mr. VanMidde’s fellow inmates told officials that Mr. VanMidde promised to kill his wife upon his release from prison, according to Rohnert Park Lt. Jeff Taylor. He was in custody after being arrested by Marin officials for a July 31 incident, in which police evacuated a sleepy suburban Rohnert Park street after learning Mr. VanMidde’s vehicle might have contained explosive materials. Police said they uncovered chemicals and a military device that simulates explosions.