A sponsor for an Alcoholics Anonymous group in Boulder is accused of sexually assaulting a member he had offered to help.Longmont police arrested Laureano Sifuentes, 64, Wednesday night on suspicion of unlawful sexual contact. Sifuentes posted bond Thursday morning.Boulder detectives have been investigating Sifuentes since November 2011 when a woman reported that Sifuentes had touched her inappropriately during a meeting that he had scheduled at a Boulder hotel.The woman said he persuaded two women in the AA group that he would help them through one of the AA steps. That step is about disclosing information about past wrongs to one other person, and it's usually done one-on-one in a private setting, Boulder police spokeswoman Kim Kobel said.Sifuentes arranged a meeting at a hotel in Boulder and the victim, along with another female in the AA group, agreed to attend, Kobel said.The victim said that during their meeting, Sifuentes touched her sexually. She fled the hotel and called to have someone pick her up at another location.The other woman did not see what allegedly occurred, but did observe the alleged victim fleeing the hotel, Boulder police said.Sifuentes has previous arrests in 1998 and 2000 for driving under the influence of alcohol.Anyone with information about this case is asked to call Detective Colleen Wilcox at 303-441-4483. Those who have information but wish to remain anonymous may contact the Northern Colorado Crime Stoppers at 1-800-222-TIPS (8477) or 1-800-444-3776.Tips can also be submitted through the Crime Stoppers website. Those submitting tips through Crime Stoppers that lead to the arrest and filing of charges on a suspect(s) may be eligible for a cash reward of up to $1,000 from Crime Stoppers.