(AP) - The lead singer of As I Lay Dying, who is accused of trying to hire a hit man to kill his wife, was showing changes in behavior that concerned her, she said in divorce papers. Tim Lambesis was arrested Tuesday while he was shopping at a store in Oceanside. Law enforcement officials said they acted after receiving a tip last week that the 32-year-old frontman of the Grammy-nominated band - who is covered in tattoos and known for his growling voice - was plotting to kill his wife, who filed for divorce in September. Authorities said he tried to hire an undercover detective who he believed was a hit man. In divorce papers, Meggan Lambesis said she was concerned about changes in her husband's behavior in regards to his ability to care for their three children, but the homemaker gave no indication she felt in danger. The couple adopted the children - ages 4, 8 and 10 - from Ethiopia, and Tim Lambesis continued to see them for about 10 hours a week when he was not on tour, even though the couple was no longer living together, according to court documents. Meggan Lambesis said her estranged husband had become "obsessed with bodybuilding" and was distracted while with the children, often texting or talking on the phone. She noted he had fallen asleep while watching them at the beach or near the pool and said they need a "stable parent" to help them adjust to their new life and country. She said he tours six months out of the year and had traveled across the country twice in one year to visit a girlfriend. She said he also had spent thousands of dollars on tattoos. Both had agreed to private mediation to discuss the children's custody. Comments by Tim Lambesis about the band's latest album, "Awakened," indicate he may have been struggling. The band's website says the album - released the same month his wife filed for divorce - is a "far darker, more pessimistic beast" compared to previous albums. "On this record, I wasn't purposefully trying to be negative, but I think sometimes we have to be honest with some of the darker and more difficult times of our lives to get back to that positivity," Lambesis is quoted as saying. While the lyrics do perhaps seem like a dark window into my soul, they're written that way specifically because I want to move on and transcend those difficult moments in life. Authorities said a task force from several law enforcement agencies launched an investigation that led to the arrest late Tuesday. The department would give no further details. A man who answered the phone at a number listed in the singer's name in Del Mar said the family was not commenting at this time. Lambesis was scheduled to be arraigned Thursday in Vista. His attorney could not be reached for comment. The band, which plays in an aggressive style that features metal guitar riffs at the furious pace of hardcore punk, was scheduled to tour the country this summer. Lambesis' record label, Metal Blade, said in a message posted to the band's fans that "there are many unanswered questions, and the situation will become clearer in the coming days and weeks." "We'll keep you informed as best we can," the message said. Our thoughts right now are with Tim, his family, and with everyone else affected by this terrible situation - and with our fans, whom we love and draw strength from.