Waterloo Police say that a man was arrested after holding a woman and several children against their will in a hostage situation and standoff Tuesday morning. 40-year old Robert Smull is in custody after the events that happened in the 700 block of Kern Street that blocked off the street for part of the morning. Police first responded to the residence around 8:30 a.m. and found Smull barricaded with the woman and children inside. According to Police Chief Joel Fitzgerald, the Waterloo Police Tactical Unit, hostage negotiators, and Crisis Intervention Unit all responded to the scene. After several hours of negotiation, the woman and children were able to get out of the house. Smull has been charged with first degree domestic assault, fourth degree criminal mischief, and probation violation.